diff --git a/crates/cli/src/commands/config.rs b/crates/cli/src/commands/config.rs
index afbdf8a4..a1b57d3e 100644
--- a/crates/cli/src/commands/config.rs
+++ b/crates/cli/src/commands/config.rs
@@ -310,6 +310,8 @@ async fn sync(root: &super::Options, prune: bool, dry_run: bool) -> anyhow::Resu
                         jwks_uri_override: provider.jwks_uri,
                         discovery_mode,
                         pkce_mode,
+                        // TODO: get that from the config
+                        additional_authorization_parameters: Vec::new(),
                     },
                 )
                 .await?;
diff --git a/crates/data-model/src/upstream_oauth2/provider.rs b/crates/data-model/src/upstream_oauth2/provider.rs
index e9aea449..af0d26bc 100644
--- a/crates/data-model/src/upstream_oauth2/provider.rs
+++ b/crates/data-model/src/upstream_oauth2/provider.rs
@@ -142,6 +142,7 @@ pub struct UpstreamOAuthProvider {
     pub token_endpoint_auth_method: OAuthClientAuthenticationMethod,
     pub created_at: DateTime<Utc>,
     pub claims_imports: ClaimsImports,
+    pub additional_authorization_parameters: Vec<(String, String)>,
 }
 
 /// Whether to set the email as verified when importing it from the upstream
diff --git a/crates/handlers/src/upstream_oauth2/cache.rs b/crates/handlers/src/upstream_oauth2/cache.rs
index cf10280a..69fcc857 100644
--- a/crates/handlers/src/upstream_oauth2/cache.rs
+++ b/crates/handlers/src/upstream_oauth2/cache.rs
@@ -505,6 +505,7 @@ mod tests {
             token_endpoint_auth_method: OAuthClientAuthenticationMethod::None,
             created_at: clock.now(),
             claims_imports: UpstreamOAuthProviderClaimsImports::default(),
+            additional_authorization_parameters: Vec::new(),
         };
 
         // Without any override, it should just use discovery
diff --git a/crates/handlers/src/upstream_oauth2/link.rs b/crates/handlers/src/upstream_oauth2/link.rs
index b03c02f5..4719e7e2 100644
--- a/crates/handlers/src/upstream_oauth2/link.rs
+++ b/crates/handlers/src/upstream_oauth2/link.rs
@@ -925,6 +925,7 @@ mod tests {
                     jwks_uri_override: None,
                     discovery_mode: mas_data_model::UpstreamOAuthProviderDiscoveryMode::Oidc,
                     pkce_mode: mas_data_model::UpstreamOAuthProviderPkceMode::Auto,
+                    additional_authorization_parameters: Vec::new(),
                 },
             )
             .await
diff --git a/crates/handlers/src/views/login.rs b/crates/handlers/src/views/login.rs
index fdca38dd..513a9327 100644
--- a/crates/handlers/src/views/login.rs
+++ b/crates/handlers/src/views/login.rs
@@ -363,6 +363,7 @@ mod test {
                     jwks_uri_override: None,
                     discovery_mode: mas_data_model::UpstreamOAuthProviderDiscoveryMode::Oidc,
                     pkce_mode: mas_data_model::UpstreamOAuthProviderPkceMode::Auto,
+                    additional_authorization_parameters: Vec::new(),
                 },
             )
             .await
@@ -397,6 +398,7 @@ mod test {
                     jwks_uri_override: None,
                     discovery_mode: mas_data_model::UpstreamOAuthProviderDiscoveryMode::Oidc,
                     pkce_mode: mas_data_model::UpstreamOAuthProviderPkceMode::Auto,
+                    additional_authorization_parameters: Vec::new(),
                 },
             )
             .await
diff --git a/crates/storage-pg/.sqlx/query-21132afc29be5394a03680dd27d2aff5e2249a973083c0675935dc658f73b1f4.json b/crates/storage-pg/.sqlx/query-21132afc29be5394a03680dd27d2aff5e2249a973083c0675935dc658f73b1f4.json
new file mode 100644
index 00000000..403bee8e
--- /dev/null
+++ b/crates/storage-pg/.sqlx/query-21132afc29be5394a03680dd27d2aff5e2249a973083c0675935dc658f73b1f4.json
@@ -0,0 +1,38 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "\n                INSERT INTO upstream_oauth_providers (\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    token_endpoint_auth_method,\n                    token_endpoint_signing_alg,\n                    client_id,\n                    encrypted_client_secret,\n                    claims_imports,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    jwks_uri_override,\n                    discovery_mode,\n                    pkce_mode,\n                    additional_parameters,\n                    created_at\n                ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9,\n                          $10, $11, $12, $13, $14, $15, $16, $17)\n                ON CONFLICT (upstream_oauth_provider_id) \n                    DO UPDATE\n                    SET\n                        issuer = EXCLUDED.issuer,\n                        human_name = EXCLUDED.human_name,\n                        brand_name = EXCLUDED.brand_name,\n                        scope = EXCLUDED.scope,\n                        token_endpoint_auth_method = EXCLUDED.token_endpoint_auth_method,\n                        token_endpoint_signing_alg = EXCLUDED.token_endpoint_signing_alg,\n                        client_id = EXCLUDED.client_id,\n                        encrypted_client_secret = EXCLUDED.encrypted_client_secret,\n                        claims_imports = EXCLUDED.claims_imports,\n                        authorization_endpoint_override = EXCLUDED.authorization_endpoint_override,\n                        token_endpoint_override = EXCLUDED.token_endpoint_override,\n                        jwks_uri_override = EXCLUDED.jwks_uri_override,\n                        discovery_mode = EXCLUDED.discovery_mode,\n                        pkce_mode = EXCLUDED.pkce_mode,\n                        additional_parameters = EXCLUDED.additional_parameters\n                RETURNING created_at\n            ",
+  "describe": {
+    "columns": [
+      {
+        "ordinal": 0,
+        "name": "created_at",
+        "type_info": "Timestamptz"
+      }
+    ],
+    "parameters": {
+      "Left": [
+        "Uuid",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Jsonb",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Text",
+        "Jsonb",
+        "Timestamptz"
+      ]
+    },
+    "nullable": [
+      false
+    ]
+  },
+  "hash": "21132afc29be5394a03680dd27d2aff5e2249a973083c0675935dc658f73b1f4"
+}
diff --git a/crates/storage-pg/.sqlx/query-4668abf6520ecca2fa71a26b02d206600624bbba57985d4a7fba2763478cd065.json b/crates/storage-pg/.sqlx/query-4668abf6520ecca2fa71a26b02d206600624bbba57985d4a7fba2763478cd065.json
deleted file mode 100644
index 0752d5a6..00000000
--- a/crates/storage-pg/.sqlx/query-4668abf6520ecca2fa71a26b02d206600624bbba57985d4a7fba2763478cd065.json
+++ /dev/null
@@ -1,37 +0,0 @@
-{
-  "db_name": "PostgreSQL",
-  "query": "\n                INSERT INTO upstream_oauth_providers (\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    token_endpoint_auth_method,\n                    token_endpoint_signing_alg,\n                    client_id,\n                    encrypted_client_secret,\n                    claims_imports,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    jwks_uri_override,\n                    discovery_mode,\n                    pkce_mode,\n                    created_at\n                ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9,\n                          $10, $11, $12, $13, $14, $15, $16)\n                ON CONFLICT (upstream_oauth_provider_id) \n                    DO UPDATE\n                    SET\n                        issuer = EXCLUDED.issuer,\n                        human_name = EXCLUDED.human_name,\n                        brand_name = EXCLUDED.brand_name,\n                        scope = EXCLUDED.scope,\n                        token_endpoint_auth_method = EXCLUDED.token_endpoint_auth_method,\n                        token_endpoint_signing_alg = EXCLUDED.token_endpoint_signing_alg,\n                        client_id = EXCLUDED.client_id,\n                        encrypted_client_secret = EXCLUDED.encrypted_client_secret,\n                        claims_imports = EXCLUDED.claims_imports,\n                        authorization_endpoint_override = EXCLUDED.authorization_endpoint_override,\n                        token_endpoint_override = EXCLUDED.token_endpoint_override,\n                        jwks_uri_override = EXCLUDED.jwks_uri_override,\n                        discovery_mode = EXCLUDED.discovery_mode,\n                        pkce_mode = EXCLUDED.pkce_mode\n                RETURNING created_at\n            ",
-  "describe": {
-    "columns": [
-      {
-        "ordinal": 0,
-        "name": "created_at",
-        "type_info": "Timestamptz"
-      }
-    ],
-    "parameters": {
-      "Left": [
-        "Uuid",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Jsonb",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Text",
-        "Timestamptz"
-      ]
-    },
-    "nullable": [
-      false
-    ]
-  },
-  "hash": "4668abf6520ecca2fa71a26b02d206600624bbba57985d4a7fba2763478cd065"
-}
diff --git a/crates/storage-pg/.sqlx/query-2098ff49e9f4b847543b3186dbc4a8cdf1d21f788a533477c233455c57a1b755.json b/crates/storage-pg/.sqlx/query-ccf4965aa84c497ac9759cb31f3ecba59fdf18085791f799dfd398bef4f8eb8c.json
similarity index 86%
rename from crates/storage-pg/.sqlx/query-2098ff49e9f4b847543b3186dbc4a8cdf1d21f788a533477c233455c57a1b755.json
rename to crates/storage-pg/.sqlx/query-ccf4965aa84c497ac9759cb31f3ecba59fdf18085791f799dfd398bef4f8eb8c.json
index 06940c1a..a30ed5c7 100644
--- a/crates/storage-pg/.sqlx/query-2098ff49e9f4b847543b3186dbc4a8cdf1d21f788a533477c233455c57a1b755.json
+++ b/crates/storage-pg/.sqlx/query-ccf4965aa84c497ac9759cb31f3ecba59fdf18085791f799dfd398bef4f8eb8c.json
@@ -1,6 +1,6 @@
 {
   "db_name": "PostgreSQL",
-  "query": "\n                SELECT\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    client_id,\n                    encrypted_client_secret,\n                    token_endpoint_signing_alg,\n                    token_endpoint_auth_method,\n                    created_at,\n                    claims_imports as \"claims_imports: Json<UpstreamOAuthProviderClaimsImports>\",\n                    jwks_uri_override,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    discovery_mode,\n                    pkce_mode\n                FROM upstream_oauth_providers\n            ",
+  "query": "\n                SELECT\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    client_id,\n                    encrypted_client_secret,\n                    token_endpoint_signing_alg,\n                    token_endpoint_auth_method,\n                    created_at,\n                    claims_imports as \"claims_imports: Json<UpstreamOAuthProviderClaimsImports>\",\n                    jwks_uri_override,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    discovery_mode,\n                    pkce_mode,\n                    additional_parameters as \"additional_parameters: Json<Vec<(String, String)>>\"\n                FROM upstream_oauth_providers\n            ",
   "describe": {
     "columns": [
       {
@@ -82,6 +82,11 @@
         "ordinal": 15,
         "name": "pkce_mode",
         "type_info": "Text"
+      },
+      {
+        "ordinal": 16,
+        "name": "additional_parameters: Json<Vec<(String, String)>>",
+        "type_info": "Jsonb"
       }
     ],
     "parameters": {
@@ -103,8 +108,9 @@
       true,
       true,
       false,
-      false
+      false,
+      true
     ]
   },
-  "hash": "2098ff49e9f4b847543b3186dbc4a8cdf1d21f788a533477c233455c57a1b755"
+  "hash": "ccf4965aa84c497ac9759cb31f3ecba59fdf18085791f799dfd398bef4f8eb8c"
 }
diff --git a/crates/storage-pg/.sqlx/query-eb5af2b52b65eb9fba94418075dac0ddb04752d374e1905d1d935313090375c9.json b/crates/storage-pg/.sqlx/query-d8d9e49227b7945b4c3bcd842b59a7af6a21f7e9e2d715dc6360c3d691373903.json
similarity index 85%
rename from crates/storage-pg/.sqlx/query-eb5af2b52b65eb9fba94418075dac0ddb04752d374e1905d1d935313090375c9.json
rename to crates/storage-pg/.sqlx/query-d8d9e49227b7945b4c3bcd842b59a7af6a21f7e9e2d715dc6360c3d691373903.json
index f7e51556..e923947b 100644
--- a/crates/storage-pg/.sqlx/query-eb5af2b52b65eb9fba94418075dac0ddb04752d374e1905d1d935313090375c9.json
+++ b/crates/storage-pg/.sqlx/query-d8d9e49227b7945b4c3bcd842b59a7af6a21f7e9e2d715dc6360c3d691373903.json
@@ -1,6 +1,6 @@
 {
   "db_name": "PostgreSQL",
-  "query": "\n                SELECT\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    client_id,\n                    encrypted_client_secret,\n                    token_endpoint_signing_alg,\n                    token_endpoint_auth_method,\n                    created_at,\n                    claims_imports as \"claims_imports: Json<UpstreamOAuthProviderClaimsImports>\",\n                    jwks_uri_override,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    discovery_mode,\n                    pkce_mode\n                FROM upstream_oauth_providers\n                WHERE upstream_oauth_provider_id = $1\n            ",
+  "query": "\n                SELECT\n                    upstream_oauth_provider_id,\n                    issuer,\n                    human_name,\n                    brand_name,\n                    scope,\n                    client_id,\n                    encrypted_client_secret,\n                    token_endpoint_signing_alg,\n                    token_endpoint_auth_method,\n                    created_at,\n                    claims_imports as \"claims_imports: Json<UpstreamOAuthProviderClaimsImports>\",\n                    jwks_uri_override,\n                    authorization_endpoint_override,\n                    token_endpoint_override,\n                    discovery_mode,\n                    pkce_mode,\n                    additional_parameters as \"additional_parameters: Json<Vec<(String, String)>>\"\n                FROM upstream_oauth_providers\n                WHERE upstream_oauth_provider_id = $1\n            ",
   "describe": {
     "columns": [
       {
@@ -82,6 +82,11 @@
         "ordinal": 15,
         "name": "pkce_mode",
         "type_info": "Text"
+      },
+      {
+        "ordinal": 16,
+        "name": "additional_parameters: Json<Vec<(String, String)>>",
+        "type_info": "Jsonb"
       }
     ],
     "parameters": {
@@ -105,8 +110,9 @@
       true,
       true,
       false,
-      false
+      false,
+      true
     ]
   },
-  "hash": "eb5af2b52b65eb9fba94418075dac0ddb04752d374e1905d1d935313090375c9"
+  "hash": "d8d9e49227b7945b4c3bcd842b59a7af6a21f7e9e2d715dc6360c3d691373903"
 }
diff --git a/crates/storage-pg/migrations/20240301091201_upstream_oauth_additional_parameters.sql b/crates/storage-pg/migrations/20240301091201_upstream_oauth_additional_parameters.sql
new file mode 100644
index 00000000..e941636f
--- /dev/null
+++ b/crates/storage-pg/migrations/20240301091201_upstream_oauth_additional_parameters.sql
@@ -0,0 +1,18 @@
+-- Copyright 2024 The Matrix.org Foundation C.I.C.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+-- Adds a column to the upstream_oauth_providers table to store additional parameters to be sent to the OAuth provider.
+-- Parameters are stored as [["key", "value"], ["key", "value"], ...] in a JSONB column to keep key ordering.
+ALTER TABLE upstream_oauth_providers 
+    ADD COLUMN additional_parameters JSONB;
diff --git a/crates/storage-pg/src/iden.rs b/crates/storage-pg/src/iden.rs
index 194d335c..18f745e5 100644
--- a/crates/storage-pg/src/iden.rs
+++ b/crates/storage-pg/src/iden.rs
@@ -110,6 +110,7 @@ pub enum UpstreamOAuthProviders {
     ClaimsImports,
     DiscoveryMode,
     PkceMode,
+    AdditionalParameters,
     JwksUriOverride,
     TokenEndpointOverride,
     AuthorizationEndpointOverride,
diff --git a/crates/storage-pg/src/upstream_oauth2/mod.rs b/crates/storage-pg/src/upstream_oauth2/mod.rs
index 2876fe55..3b41998f 100644
--- a/crates/storage-pg/src/upstream_oauth2/mod.rs
+++ b/crates/storage-pg/src/upstream_oauth2/mod.rs
@@ -76,6 +76,7 @@ mod tests {
                     jwks_uri_override: None,
                     discovery_mode: mas_data_model::UpstreamOAuthProviderDiscoveryMode::Oidc,
                     pkce_mode: mas_data_model::UpstreamOAuthProviderPkceMode::Auto,
+                    additional_authorization_parameters: Vec::new(),
                 },
             )
             .await
@@ -259,6 +260,7 @@ mod tests {
                         jwks_uri_override: None,
                         discovery_mode: mas_data_model::UpstreamOAuthProviderDiscoveryMode::Oidc,
                         pkce_mode: mas_data_model::UpstreamOAuthProviderPkceMode::Auto,
+                        additional_authorization_parameters: Vec::new(),
                     },
                 )
                 .await
diff --git a/crates/storage-pg/src/upstream_oauth2/provider.rs b/crates/storage-pg/src/upstream_oauth2/provider.rs
index 8f66a1e0..a7ae86cd 100644
--- a/crates/storage-pg/src/upstream_oauth2/provider.rs
+++ b/crates/storage-pg/src/upstream_oauth2/provider.rs
@@ -67,6 +67,7 @@ struct ProviderLookup {
     token_endpoint_override: Option<String>,
     discovery_mode: String,
     pkce_mode: String,
+    additional_parameters: Option<Json<Vec<(String, String)>>>,
 }
 
 impl TryFrom<ProviderLookup> for UpstreamOAuthProvider {
@@ -143,6 +144,11 @@ impl TryFrom<ProviderLookup> for UpstreamOAuthProvider {
                 .source(e)
         })?;
 
+        let additional_authorization_parameters = value
+            .additional_parameters
+            .map(|Json(x)| x)
+            .unwrap_or_default();
+
         Ok(UpstreamOAuthProvider {
             id,
             issuer: value.issuer,
@@ -160,6 +166,7 @@ impl TryFrom<ProviderLookup> for UpstreamOAuthProvider {
             jwks_uri_override,
             discovery_mode,
             pkce_mode,
+            additional_authorization_parameters,
         })
     }
 }
@@ -197,7 +204,8 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
                     authorization_endpoint_override,
                     token_endpoint_override,
                     discovery_mode,
-                    pkce_mode
+                    pkce_mode,
+                    additional_parameters as "additional_parameters: Json<Vec<(String, String)>>"
                 FROM upstream_oauth_providers
                 WHERE upstream_oauth_provider_id = $1
             "#,
@@ -305,6 +313,7 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
             jwks_uri_override: params.jwks_uri_override,
             discovery_mode: params.discovery_mode,
             pkce_mode: params.pkce_mode,
+            additional_authorization_parameters: params.additional_authorization_parameters,
         })
     }
 
@@ -411,9 +420,10 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
                     jwks_uri_override,
                     discovery_mode,
                     pkce_mode,
+                    additional_parameters,
                     created_at
                 ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9,
-                          $10, $11, $12, $13, $14, $15, $16)
+                          $10, $11, $12, $13, $14, $15, $16, $17)
                 ON CONFLICT (upstream_oauth_provider_id) 
                     DO UPDATE
                     SET
@@ -430,7 +440,8 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
                         token_endpoint_override = EXCLUDED.token_endpoint_override,
                         jwks_uri_override = EXCLUDED.jwks_uri_override,
                         discovery_mode = EXCLUDED.discovery_mode,
-                        pkce_mode = EXCLUDED.pkce_mode
+                        pkce_mode = EXCLUDED.pkce_mode,
+                        additional_parameters = EXCLUDED.additional_parameters
                 RETURNING created_at
             "#,
             Uuid::from(id),
@@ -457,6 +468,7 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
             params.jwks_uri_override.as_ref().map(ToString::to_string),
             params.discovery_mode.as_str(),
             params.pkce_mode.as_str(),
+            Json(&params.additional_authorization_parameters) as _,
             created_at,
         )
         .traced()
@@ -480,6 +492,7 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
             jwks_uri_override: params.jwks_uri_override,
             discovery_mode: params.discovery_mode,
             pkce_mode: params.pkce_mode,
+            additional_authorization_parameters: params.additional_authorization_parameters,
         })
     }
 
@@ -607,6 +620,13 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
                 )),
                 ProviderLookupIden::PkceMode,
             )
+            .expr_as(
+                Expr::col((
+                    UpstreamOAuthProviders::Table,
+                    UpstreamOAuthProviders::AdditionalParameters,
+                )),
+                ProviderLookupIden::AdditionalParameters,
+            )
             .from(UpstreamOAuthProviders::Table)
             .generate_pagination(
                 (
@@ -691,7 +711,8 @@ impl<'c> UpstreamOAuthProviderRepository for PgUpstreamOAuthProviderRepository<'
                     authorization_endpoint_override,
                     token_endpoint_override,
                     discovery_mode,
-                    pkce_mode
+                    pkce_mode,
+                    additional_parameters as "additional_parameters: Json<Vec<(String, String)>>"
                 FROM upstream_oauth_providers
             "#,
         )
diff --git a/crates/storage/src/upstream_oauth2/provider.rs b/crates/storage/src/upstream_oauth2/provider.rs
index 5de174ae..3458bfa8 100644
--- a/crates/storage/src/upstream_oauth2/provider.rs
+++ b/crates/storage/src/upstream_oauth2/provider.rs
@@ -74,6 +74,9 @@ pub struct UpstreamOAuthProviderParams {
 
     /// How should PKCE be used
     pub pkce_mode: UpstreamOAuthProviderPkceMode,
+
+    /// Additional parameters to include in the authorization request
+    pub additional_authorization_parameters: Vec<(String, String)>,
 }
 
 /// Filter parameters for listing upstream OAuth 2.0 providers