diff --git a/Makefile b/Makefile
index 041dd35b..6937b025 100644
--- a/Makefile
+++ b/Makefile
@@ -15,7 +15,6 @@ TEST_ORG_REPO ?=
 TEST_EPHEMERAL ?= false
 SYNC_PERIOD ?= 1m
 USE_RUNNERSET ?=
-RUNNER_FEATURE_FLAG_EPHEMERAL ?=
 KUBECONTEXT ?= kind-acceptance
 CLUSTER ?= acceptance
 CERT_MANAGER_VERSION ?= v1.1.1
@@ -188,7 +187,6 @@ acceptance/deploy:
 	TEST_ORG=${TEST_ORG} TEST_ORG_REPO=${TEST_ORG_REPO} SYNC_PERIOD=${SYNC_PERIOD} \
 	USE_RUNNERSET=${USE_RUNNERSET} \
 	TEST_EPHEMERAL=${TEST_EPHEMERAL} \
-	RUNNER_FEATURE_FLAG_EPHEMERAL=${RUNNER_FEATURE_FLAG_EPHEMERAL} \
 	acceptance/deploy.sh
 
 acceptance/tests:
diff --git a/acceptance/testdata/runnerdeploy.envsubst.yaml b/acceptance/testdata/runnerdeploy.envsubst.yaml
index ae6375e7..3b1552b6 100644
--- a/acceptance/testdata/runnerdeploy.envsubst.yaml
+++ b/acceptance/testdata/runnerdeploy.envsubst.yaml
@@ -19,11 +19,6 @@ spec:
 
       ephemeral: ${TEST_EPHEMERAL}
 
-      # Whether to pass --ephemeral (true) or --once (false, deprecated)
-      env:
-      - name: RUNNER_FEATURE_FLAG_EPHEMERAL
-        value: "${RUNNER_FEATURE_FLAG_EPHEMERAL}"
-
       #
       # dockerd within runner container
       #
diff --git a/acceptance/testdata/runnerset.envsubst.yaml b/acceptance/testdata/runnerset.envsubst.yaml
index cf39378f..ba6d705e 100644
--- a/acceptance/testdata/runnerset.envsubst.yaml
+++ b/acceptance/testdata/runnerset.envsubst.yaml
@@ -59,9 +59,6 @@ spec:
       containers:
       - name: runner
         imagePullPolicy: IfNotPresent
-        env:
-        - name: RUNNER_FEATURE_FLAG_EPHEMERAL
-          value: "${RUNNER_FEATURE_FLAG_EPHEMERAL}"
       #- name: docker
       #  #image: mumoshu/actions-runner-dind:dev
 ---
diff --git a/controllers/new_runner_pod_test.go b/controllers/new_runner_pod_test.go
index 84b4767b..8ff7efc9 100644
--- a/controllers/new_runner_pod_test.go
+++ b/controllers/new_runner_pod_test.go
@@ -106,10 +106,6 @@ func TestNewRunnerPod(t *testing.T) {
 							Name:  "DOCKER_CERT_PATH",
 							Value: "/certs/client",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 					},
 					VolumeMounts: []corev1.VolumeMount{
 						{
@@ -228,10 +224,6 @@ func TestNewRunnerPod(t *testing.T) {
 							Name:  "RUNNER_EPHEMERAL",
 							Value: "true",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 					},
 					VolumeMounts: []corev1.VolumeMount{
 						{
@@ -310,10 +302,6 @@ func TestNewRunnerPod(t *testing.T) {
 							Name:  "RUNNER_EPHEMERAL",
 							Value: "true",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 					},
 					VolumeMounts: []corev1.VolumeMount{
 						{
@@ -532,10 +520,6 @@ func TestNewRunnerPodFromRunnerController(t *testing.T) {
 							Name:  "DOCKER_CERT_PATH",
 							Value: "/certs/client",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 						{
 							Name:  "RUNNER_NAME",
 							Value: "runner",
@@ -669,10 +653,6 @@ func TestNewRunnerPodFromRunnerController(t *testing.T) {
 							Name:  "RUNNER_EPHEMERAL",
 							Value: "true",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 						{
 							Name:  "RUNNER_NAME",
 							Value: "runner",
@@ -770,10 +750,6 @@ func TestNewRunnerPodFromRunnerController(t *testing.T) {
 							Name:  "RUNNER_EPHEMERAL",
 							Value: "true",
 						},
-						{
-							Name:  "RUNNER_FEATURE_FLAG_EPHEMERAL",
-							Value: "true",
-						},
 						{
 							Name:  "RUNNER_NAME",
 							Value: "runner",
diff --git a/controllers/runner_controller.go b/controllers/runner_controller.go
index 6cb9a9cb..a1c15c59 100644
--- a/controllers/runner_controller.go
+++ b/controllers/runner_controller.go
@@ -50,12 +50,11 @@ const (
 	// This is an annotation internal to actions-runner-controller and can change in backward-incompatible ways
 	annotationKeyRegistrationOnly = "actions-runner-controller/registration-only"
 
-	EnvVarOrg                        = "RUNNER_ORG"
-	EnvVarRepo                       = "RUNNER_REPO"
-	EnvVarEnterprise                 = "RUNNER_ENTERPRISE"
-	EnvVarEphemeral                  = "RUNNER_EPHEMERAL"
-	EnvVarRunnerFeatureFlagEphemeral = "RUNNER_FEATURE_FLAG_EPHEMERAL"
-	EnvVarTrue                       = "true"
+	EnvVarOrg        = "RUNNER_ORG"
+	EnvVarRepo       = "RUNNER_REPO"
+	EnvVarEnterprise = "RUNNER_ENTERPRISE"
+	EnvVarEphemeral  = "RUNNER_EPHEMERAL"
+	EnvVarTrue       = "true"
 )
 
 // RunnerReconciler reconciles a Runner object
@@ -830,12 +829,6 @@ func newRunnerPod(runnerName string, template corev1.Pod, runnerSpec v1alpha1.Ru
 		}
 	}
 
-	// TODO Remove this once we remove RUNNER_FEATURE_FLAG_EPHEMERAL from runner's entrypoint.sh
-	// and make --ephemeral the default option.
-	if getRunnerEnv(pod, EnvVarRunnerFeatureFlagEphemeral) == "" {
-		setRunnerEnv(pod, EnvVarRunnerFeatureFlagEphemeral, EnvVarTrue)
-	}
-
 	return *pod, nil
 }
 
diff --git a/test/e2e/e2e_test.go b/test/e2e/e2e_test.go
index 0d6791c3..897a73a5 100644
--- a/test/e2e/e2e_test.go
+++ b/test/e2e/e2e_test.go
@@ -198,7 +198,6 @@ type env struct {
 	githubTokenWebhook                                       string
 	testEnterprise                                           string
 	testEphemeral                                            string
-	featureFlagEphemeral                                     *bool
 	scaleDownDelaySecondsAfterScaleOut                       int64
 	minReplicas                                              int64
 	dockerdWithinRunnerContainer                             bool
@@ -234,10 +233,6 @@ func initTestEnv(t *testing.T) *env {
 	e.testEphemeral = testing.Getenv(t, "TEST_EPHEMERAL", "")
 	e.testJobs = createTestJobs(id, testResultCMNamePrefix, 20)
 
-	if ephemeral, err := strconv.ParseBool(testing.Getenv(t, "TEST_FEATURE_FLAG_EPHEMERAL", "")); err == nil {
-		e.featureFlagEphemeral = &ephemeral
-	}
-
 	e.scaleDownDelaySecondsAfterScaleOut, _ = strconv.ParseInt(testing.Getenv(t, "TEST_RUNNER_SCALE_DOWN_DELAY_SECONDS_AFTER_SCALE_OUT", "10"), 10, 32)
 	e.minReplicas, _ = strconv.ParseInt(testing.Getenv(t, "TEST_RUNNER_MIN_REPLICAS", "1"), 10, 32)
 
@@ -308,10 +303,6 @@ func (e *env) installActionsRunnerController(t *testing.T) {
 		fmt.Sprintf("ENTERPRISE_RUNNER_MIN_REPLICAS=%d", e.minReplicas),
 	}
 
-	if e.featureFlagEphemeral != nil {
-		varEnv = append(varEnv, fmt.Sprintf("RUNNER_FEATURE_FLAG_EPHEMERAL=%v", *e.featureFlagEphemeral))
-	}
-
 	if e.useApp {
 		varEnv = append(varEnv,
 			"ACCEPTANCE_TEST_SECRET_TYPE=app",