diff --git a/.ci/scripts/calculate_jobs.py b/.ci/scripts/calculate_jobs.py
index ea278173db386eaac0d4d984d2b5f8517adb0778..5249acdc5d67a5d7d7a19e616651c07aea1bd4d1 100755
--- a/.ci/scripts/calculate_jobs.py
+++ b/.ci/scripts/calculate_jobs.py
@@ -60,7 +60,7 @@ trial_postgres_tests = [
     {
         "python-version": "3.9",
         "database": "postgres",
-        "postgres-version": "11",
+        "postgres-version": "13",
         "extras": "all",
     }
 ]
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d91f9c291876644befaf0b1f32dea17b5b27367a..084b08b2492dd0909f5fab8d8e5b15feca3e393c 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -581,7 +581,7 @@ jobs:
       matrix:
         include:
           - python-version: "3.9"
-            postgres-version: "11"
+            postgres-version: "13"
 
           - python-version: "3.13"
             postgres-version: "17"
diff --git a/changelog.d/18034.removal b/changelog.d/18034.removal
new file mode 100644
index 0000000000000000000000000000000000000000..303b442fd4ac9921b44ceac4b46a063956b3a3cd
--- /dev/null
+++ b/changelog.d/18034.removal
@@ -0,0 +1 @@
+Remove support for PostgreSQL 11 and 12. Contributed by @clokep.
diff --git a/docs/upgrade.md b/docs/upgrade.md
index 45e63b0c5de87274fa2c49839d8d9ca6de3ae3cb..6c96cb91a31b5ca3fab462f8c4c240f734b4ffd6 100644
--- a/docs/upgrade.md
+++ b/docs/upgrade.md
@@ -117,6 +117,14 @@ each upgrade are complete before moving on to the next upgrade, to avoid
 stacking them up. You can monitor the currently running background updates with
 [the Admin API](usage/administration/admin_api/background_updates.html#status).
 
+# Upgrading to v1.122.0
+
+## Dropping support for PostgreSQL 11 and 12
+
+In line with our [deprecation policy](deprecation_policy.md), we've dropped
+support for PostgreSQL 11 and 12, as they are no longer supported upstream.
+This release of Synapse requires PostgreSQL 13+.
+
 # Upgrading to v1.120.0
 
 ## Removal of experimental MSC3886 feature
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index 8c8c6d041448d794bc4a91b970653cc63bb48a22..e4cd359201b971b469700de7ab70f3bb1dc91491 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -99,8 +99,8 @@ class PostgresEngine(
         allow_unsafe_locale = self.config.get("allow_unsafe_locale", False)
 
         # Are we on a supported PostgreSQL version?
-        if not allow_outdated_version and self._version < 110000:
-            raise RuntimeError("Synapse requires PostgreSQL 11 or above.")
+        if not allow_outdated_version and self._version < 130000:
+            raise RuntimeError("Synapse requires PostgreSQL 13 or above.")
 
         with db_conn.cursor() as txn:
             txn.execute("SHOW SERVER_ENCODING")