diff --git a/pkg/receive/handler.go b/pkg/receive/handler.go
index b2fdd382178..1ef2b8cbc9f 100644
--- a/pkg/receive/handler.go
+++ b/pkg/receive/handler.go
@@ -924,15 +924,16 @@ func (h *Handler) distributeTimeseriesToReplicas(
 	for tsIndex, ts := range timeseries {
 		var tenant = tenantHTTP
 
-		if h.splitTenantLabelName != "" {
+		// Only extract tenant from split label when running as a router.
+		// Ingestors should use the tenant determined by the router.
+		if h.splitTenantLabelName != "" && h.receiverMode != IngestorOnly {
 			lbls := labelpb.ZLabelsToPromLabels(ts.Labels)
 
 			tenantLabel := lbls.Get(h.splitTenantLabelName)
 			if tenantLabel != "" {
 				tenant = h.splitTenantLabelName + ":" + tenantLabel
-			} else {
-				tenant = h.options.DefaultTenantID
 			}
+			// If tenant label doesn't exist, keep the tenant from HTTP header (tenantHTTP)
 		}
 
 		for _, rn := range replicas {
@@ -1017,11 +1018,14 @@ func (h *Handler) sendLocalWrite(
 	tenantSeriesMapping := map[string][]prompb.TimeSeries{}
 	for _, ts := range trackedSeries.timeSeries {
 		var tenant = tenantHTTP
-		if h.splitTenantLabelName != "" {
+		// Only extract tenant from split label when running as a router.
+		// Ingestors should use the tenant determined by the router.
+		if h.splitTenantLabelName != "" && h.receiverMode != IngestorOnly {
 			lbls := labelpb.ZLabelsToPromLabels(ts.Labels)
 			if tnt := lbls.Get(h.splitTenantLabelName); tnt != "" {
-				tenant = tnt
+				tenant = h.splitTenantLabelName + ":" + tnt
 			}
+			// If tenant label doesn't exist, keep the tenant from HTTP header (tenantHTTP)
 		}
 		tenantSeriesMapping[tenant] = append(tenantSeriesMapping[tenant], ts)
 	}
diff --git a/test/e2e/receive_test.go b/test/e2e/receive_test.go
index c938a4f0407..f5a5609b389 100644
--- a/test/e2e/receive_test.go
+++ b/test/e2e/receive_test.go
@@ -1052,8 +1052,8 @@ func TestReceiveExtractsTenant(t *testing.T) {
 				Timeseries: []prompb.TimeSeries{
 					{
 						Labels: []prompb.Label{
-							{Name: tenantLabelName, Value: "tenant-1"},
 							{Name: "aa", Value: "bb"},
+							{Name: tenantLabelName, Value: "tenant-1"},
 						},
 						Samples: []prompb.Sample{
 							{Value: 1, Timestamp: time.Now().UnixMilli()},
@@ -1063,7 +1063,7 @@ func TestReceiveExtractsTenant(t *testing.T) {
 			})
 		}))
 
-		testutil.Ok(t, i.WaitSumMetricsWithOptions(e2emon.Equals(0), []string{"prometheus_tsdb_blocks_loaded"}, e2emon.WithLabelMatchers(matchers.MustNewMatcher(matchers.MatchEqual, "tenant", "tenant-1")), e2emon.WaitMissingMetrics()))
+		testutil.Ok(t, i.WaitSumMetricsWithOptions(e2emon.Equals(0), []string{"prometheus_tsdb_blocks_loaded"}, e2emon.WithLabelMatchers(matchers.MustNewMatcher(matchers.MatchEqual, "tenant", tenantLabelName+":tenant-1")), e2emon.WaitMissingMetrics()))
 	})
 
 	t.Run("tenant label is extracted from one series, default is used for the other one", func(t *testing.T) {
@@ -1072,8 +1072,8 @@ func TestReceiveExtractsTenant(t *testing.T) {
 				Timeseries: []prompb.TimeSeries{
 					{
 						Labels: []prompb.Label{
-							{Name: tenantLabelName, Value: "tenant-2"},
 							{Name: "aa", Value: "bb"},
+							{Name: tenantLabelName, Value: "tenant-2"},
 						},
 						Samples: []prompb.Sample{
 							{Value: 1, Timestamp: time.Now().UnixMilli()},
@@ -1101,8 +1101,8 @@ func TestReceiveExtractsTenant(t *testing.T) {
 				Timeseries: []prompb.TimeSeries{
 					{
 						Labels: []prompb.Label{
-							{Name: tenantLabelName, Value: "tenant-3"},
 							{Name: "aa", Value: "bb"},
+							{Name: tenantLabelName, Value: "tenant-3"},
 						},
 						Samples: []prompb.Sample{
 							{Value: 1, Timestamp: time.Now().UnixMilli()},
@@ -1149,7 +1149,7 @@ func TestReceiveExtractsTenant(t *testing.T) {
 		}))
 
 		testutil.Ok(t, i.WaitSumMetricsWithOptions(e2emon.Equals(0), []string{"prometheus_tsdb_blocks_loaded"}, e2emon.WithLabelMatchers(matchers.MustNewMatcher(matchers.MatchEqual, "tenant", "http-tenant")), e2emon.WaitMissingMetrics()))
-		testutil.Ok(t, i.WaitSumMetricsWithOptions(e2emon.Equals(0), []string{"prometheus_tsdb_blocks_loaded"}, e2emon.WithLabelMatchers(matchers.MustNewMatcher(matchers.MatchEqual, "tenant", "tenant-3")), e2emon.WaitMissingMetrics()))
+		testutil.Ok(t, i.WaitSumMetricsWithOptions(e2emon.Equals(0), []string{"prometheus_tsdb_blocks_loaded"}, e2emon.WithLabelMatchers(matchers.MustNewMatcher(matchers.MatchEqual, "tenant", tenantLabelName+":tenant-3")), e2emon.WaitMissingMetrics()))
 
 	})
 }