diff --git a/CHANGELOG-3.6.md b/CHANGELOG-3.6.md
index 360f25f4978..dac73f7a40d 100644
--- a/CHANGELOG-3.6.md
+++ b/CHANGELOG-3.6.md
@@ -28,3 +28,10 @@ See [code changes](https://github.com/etcd-io/etcd/compare/v3.5.0...v3.6.0).
 - Package `mvcc/buckets` was moved to `storage/schema`
 - Package `wal` was moved to `storage/wal`
 - Package `datadir` was moved to `storage/datadir`
+
+
+### Metrics, Monitoring
+
+See [List of metrics](https://etcd.io/docs/latest/metrics/) for all metrics per release.
+
+- Add [`etcd_disk_defrag_inflight`](https://github.com/etcd-io/etcd/pull/13371).
diff --git a/server/storage/backend/backend.go b/server/storage/backend/backend.go
index b7207c1717a..529f83b0f25 100644
--- a/server/storage/backend/backend.go
+++ b/server/storage/backend/backend.go
@@ -432,6 +432,8 @@ func (b *backend) Defrag() error {
 
 func (b *backend) defrag() error {
 	now := time.Now()
+	isDefragActive.Set(1)
+	defer isDefragActive.Set(0)
 
 	// TODO: make this non-blocking?
 	// lock batchTx to ensure nobody is using previous tx, and then
diff --git a/server/storage/backend/metrics.go b/server/storage/backend/metrics.go
index d9641af7ae2..9d58c00638b 100644
--- a/server/storage/backend/metrics.go
+++ b/server/storage/backend/metrics.go
@@ -83,6 +83,13 @@ var (
 		// highest bucket start of 0.01 sec * 2^16 == 655.36 sec
 		Buckets: prometheus.ExponentialBuckets(.01, 2, 17),
 	})
+
+	isDefragActive = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "etcd",
+		Subsystem: "disk",
+		Name:      "defrag_inflight",
+		Help:      "Whether or not defrag is active on the member. 1 means active, 0 means not.",
+	})
 )
 
 func init() {
@@ -92,4 +99,5 @@ func init() {
 	prometheus.MustRegister(writeSec)
 	prometheus.MustRegister(defragSec)
 	prometheus.MustRegister(snapshotTransferSec)
+	prometheus.MustRegister(isDefragActive)
 }