diff --git a/config/config.sample.php b/config/config.sample.php
index 947666e0895..f51ba51a897 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -1141,6 +1141,16 @@ $CONFIG = [
  */
 'log.backtrace' => false,
 
+/**
+ * Enables logging the PHP session ID with each log line
+ *
+ * This can be used for session-related debugging, e.g. to see when a session
+ * is ended or restarted.
+ *
+ * Defaults to ``false``.
+ */
+'log.sessionId' => false,
+
 /**
  * This uses PHP.date formatting; see https://www.php.net/manual/en/function.date.php
  *
diff --git a/lib/private/Log.php b/lib/private/Log.php
index 746e4d75b91..0787483e8f2 100644
--- a/lib/private/Log.php
+++ b/lib/private/Log.php
@@ -15,11 +15,13 @@ use OC\Log\ExceptionSerializer;
 use OCP\EventDispatcher\IEventDispatcher;
 use OCP\ILogger;
 use OCP\IRequest;
+use OCP\ISession;
 use OCP\IUserSession;
 use OCP\Log\BeforeMessageLoggedEvent;
 use OCP\Log\IDataLogger;
 use OCP\Log\IFileBased;
 use OCP\Log\IWriter;
+use OCP\Session\Exceptions\SessionNotAvailableException;
 use OCP\Support\CrashReport\IRegistry;
 use Throwable;
 use function array_merge;
@@ -170,6 +172,13 @@ class Log implements ILogger, IDataLogger {
 		if (!$hasBacktrace && $logBacktrace) {
 			$entry['backtrace'] = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
 		}
+		if ($this->config->getValue('log.sessionId', false)) {
+			try {
+				$entry['sessionId'] = \OCP\Server::get(ISession::class)->getId();
+			} catch (SessionNotAvailableException) {
+				$entry['sessionId'] = false;
+			}
+		}
 
 		try {
 			if ($level >= $minLevel) {