diff --git a/changelog/unreleased/issue-5157 b/changelog/unreleased/issue-5157
new file mode 100644
index 000000000..0b209a1cc
--- /dev/null
+++ b/changelog/unreleased/issue-5157
@@ -0,0 +1,7 @@
+Enhancement: Added `--keep-unique` flag to `forget` command
+
+Restic `forget` command can now remove duplicate snapshots with the
+`--keep-unique` flag set.
+
+https://github.com/restic/restic/issues/5157
+https://github.com/restic/restic/pull/5364
\ No newline at end of file
diff --git a/cmd/restic/cmd_forget.go b/cmd/restic/cmd_forget.go
index 976db4d0d..387b3f90a 100644
--- a/cmd/restic/cmd_forget.go
+++ b/cmd/restic/cmd_forget.go
@@ -112,6 +112,7 @@ type ForgetOptions struct {
 	WithinMonthly data.Duration
 	WithinYearly  data.Duration
 	KeepTags      data.TagLists
+	Unique        bool
 
 	UnsafeAllowRemoveAll bool
 
@@ -138,6 +139,7 @@ func (opts *ForgetOptions) AddFlags(f *pflag.FlagSet) {
 	f.VarP(&opts.WithinMonthly, "keep-within-monthly", "", "keep monthly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
 	f.VarP(&opts.WithinYearly, "keep-within-yearly", "", "keep yearly snapshots that are newer than `duration` (eg. 1y5m7d2h) relative to the latest snapshot")
 	f.Var(&opts.KeepTags, "keep-tag", "keep snapshots with this `taglist` (can be specified multiple times)")
+	f.BoolVar(&opts.Unique, "keep-unique", false, "keep the only one snapshot per tree")
 	f.BoolVar(&opts.UnsafeAllowRemoveAll, "unsafe-allow-remove-all", false, "allow deleting all snapshots of a snapshot group")
 
 	f.StringArrayVar(&opts.Hosts, "hostname", nil, "only consider snapshots with the given `hostname` (can be specified multiple times)")
@@ -233,6 +235,7 @@ func runForget(ctx context.Context, opts ForgetOptions, pruneOptions PruneOption
 			WithinMonthly: opts.WithinMonthly,
 			WithinYearly:  opts.WithinYearly,
 			Tags:          opts.KeepTags,
+			Unique:        opts.Unique,
 		}
 
 		if policy.Empty() {
diff --git a/doc/060_forget.rst b/doc/060_forget.rst
index 9dcb45531..5fd29f295 100644
--- a/doc/060_forget.rst
+++ b/doc/060_forget.rst
@@ -205,6 +205,7 @@ The ``forget`` command accepts the following policy options:
    specified duration of the latest snapshot.
 -  ``--keep-within-yearly duration`` keep all yearly snapshots made within the
    specified duration of the latest snapshot.
+-  ``--keep-unique`` keep only one snapshot per tree.
 
 .. note:: All calendar related options (``--keep-{hourly,daily,...}``) work on
     natural time boundaries and *not* relative to when you run ``forget``. Weeks
diff --git a/internal/data/snapshot_policy.go b/internal/data/snapshot_policy.go
index 1ee5af984..5708a342d 100644
--- a/internal/data/snapshot_policy.go
+++ b/internal/data/snapshot_policy.go
@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/restic/restic/internal/debug"
+	"github.com/restic/restic/internal/restic"
 )
 
 // ExpirePolicy configures which snapshots should be automatically removed.
@@ -25,6 +26,7 @@ type ExpirePolicy struct {
 	WithinMonthly Duration  // keep monthly snapshots made within this duration
 	WithinYearly  Duration  // keep yearly snapshots made within this duration
 	Tags          []TagList // keep all snapshots that include at least one of the tag lists.
+	Unique        bool      // keep the only one snapshot per tree
 }
 
 func (e ExpirePolicy) String() (s string) {
@@ -164,6 +166,15 @@ func findLatestTimestamp(list Snapshots) time.Time {
 	return latest
 }
 
+func findParentSnapshot(list Snapshots, id restic.ID) *Snapshot {
+	for _, sn := range list {
+		if sn.ID().Equal(id) {
+			return sn
+		}
+	}
+	return nil
+}
+
 // KeepReason specifies why a particular snapshot was kept, and the counters at
 // that point in the policy evaluation.
 type KeepReason struct {
@@ -288,6 +299,17 @@ func ApplyPolicy(list Snapshots, p ExpirePolicy) (keep, remove Snapshots, reason
 			}
 		}
 
+		if p.Unique {
+			if cur.Parent != nil {
+				parent := findParentSnapshot(keep, *cur.Parent)
+				if parent != nil {
+					if parent.Tree == cur.Tree {
+						keepSnap = false
+					}
+				}
+			}
+		}
+
 		if keepSnap {
 			keep = append(keep, cur)
 			kr := KeepReason{