diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index d1d880f2a1..34d061e5c6 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -21,10 +21,12 @@
 
 import logging
 from typing import TYPE_CHECKING, Any, Mapping, NoReturn, cast
+from urllib.parse import quote
 
 import psycopg2.extensions
 
 from synapse.logging import opentracing
+from synapse.logging.context import current_context
 from synapse.storage.engines._base import (
     AUTO_INCREMENT_PRIMARY_KEYPLACEHOLDER,
     BaseDatabaseEngine,
@@ -40,30 +42,47 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class _SqlCommenterCursor(psycopg2.extensions.cursor):
-    """A psycopg2 cursor that appends W3C trace context to SQL statements
-    as SQLCommenter comments when OpenTracing is active.
+def _build_sqlcommenter_comment() -> str:
+    """Build a SQLCommenter comment with the logging context and trace context.
 
-    This propagates the active span's trace context to PostgreSQL, enabling
-    database-side tracing tools to correlate server-side spans with
-    application-level traces.
+    Returns a ``/*...*/`` comment string to append to a SQL query. The
+    ``traceparent`` field is only included when a trace is actively being
+    sampled; the ``log_context`` field is always included.
 
     See:
         - https://google.github.io/sqlcommenter/spec/
         - https://opentelemetry.io/docs/specs/semconv/db/database-spans/#context-propagation
     """
+    # Per the SQLCommenter spec, keys are sorted and values are URL-encoded
+    # then wrapped in single quotes.
+    pairs: dict[str, str] = {
+        "log_context": str(current_context()),
+    }
+
+    traceparent = opentracing.get_active_span_traceparent()
+    if traceparent is not None:
+        pairs["traceparent"] = traceparent
+
+    comment = ",".join(f"{k}='{quote(v)}'" for k, v in sorted(pairs.items()))
+    return f" /*{comment}*/"
+
+
+class _SqlCommenterCursor(psycopg2.extensions.cursor):
+    """A psycopg2 cursor that appends the logging context and W3C trace context
+    to SQL statements as SQLCommenter comments.
+
+    This propagates the active span's trace context to PostgreSQL, enabling
+    database-side tracing tools to correlate server-side spans with
+    application-level traces.
+    """
 
     def execute(  # type: ignore[override]
         self,
         query: str | bytes,
         vars: Any = None,  # noqa: A002
     ) -> None:
-        # The traceparent is only added when a trace is actively being
-        # sampled, so untraced queries are not affected.
         if isinstance(query, str):
-            traceparent = opentracing.get_active_span_traceparent()
-            if traceparent is not None:
-                query = f"{query} /*traceparent='{traceparent}'*/"
+            query = f"{query}{_build_sqlcommenter_comment()}"
         return super().execute(query, vars)
 
     def executemany(  # type: ignore[override]
@@ -72,9 +91,7 @@ class _SqlCommenterCursor(psycopg2.extensions.cursor):
         vars_list: Any,  # noqa: A002
     ) -> None:
         if isinstance(query, str):
-            traceparent = opentracing.get_active_span_traceparent()
-            if traceparent is not None:
-                query = f"{query} /*traceparent='{traceparent}'*/"
+            query = f"{query}{_build_sqlcommenter_comment()}"
         return super().executemany(query, vars_list)