diff --git a/cmd/root.go b/cmd/root.go
index eda150de..c47f8688 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -141,7 +141,7 @@ func setGlobalOptionsForRootCmd(fs *pflag.FlagSet, globalOptions *config.GlobalO
 	fs.BoolVar(&globalOptions.Color, "color", false, "Output with color")
 	fs.BoolVar(&globalOptions.NoColor, "no-color", false, "Output without color")
 	fs.StringVar(&globalOptions.LogLevel, "log-level", "info", "Set log level, default info")
-	fs.StringVarP(&globalOptions.Namespace, "namespace", "n", "", "Set namespace. Uses the namespace set in the context by default, and is available in templates as {{ .Namespace }}")
+	fs.StringVarP(&globalOptions.Namespace, "namespace", "n", "", `Set namespace. Overrides "HELMFILE_NAMESPACE" OS environment variable when specified. Uses the namespace set in the context by default, and is available in templates as {{ .Namespace }}`)
 	fs.StringVarP(&globalOptions.Chart, "chart", "c", "", "Set chart. Uses the chart set in release by default, and is available in template as {{ .Chart }}")
 	fs.StringArrayVarP(&globalOptions.Selector, "selector", "l", nil, `Only run using the releases that match labels. Labels can take the form of foo=bar or foo!=bar.
 A release must match all labels in a group in order to be used. Multiple groups can be specified at once.
diff --git a/docs/cli.md b/docs/cli.md
index cbde76a3..217966b7 100644
--- a/docs/cli.md
+++ b/docs/cli.md
@@ -52,7 +52,7 @@ Flags:
       --kube-context string                   Set kubectl context. Overrides "HELMFILE_KUBE_CONTEXT" OS environment variable when specified. Uses current kubectl context by default
   -k, --kustomize-binary string               Path to the kustomize binary (default "kustomize")
       --log-level string                      Set log level, default info (default "info")
-  -n, --namespace string                      Set namespace. Uses the namespace set in the context by default, and is available in templates as {{ .Namespace }}
+  -n, --namespace string                      Set namespace. Overrides "HELMFILE_NAMESPACE" OS environment variable when specified. Uses the namespace set in the context by default, and is available in templates as {{ .Namespace }}
       --no-color                              Output without color
   -q, --quiet                                 Silence output. Equivalent to log-level warn
   -l, --selector stringArray                  Only run using the releases that match labels. Labels can take the form of foo=bar or foo!=bar.
diff --git a/docs/templating.md b/docs/templating.md
index 9a596a27..b9e9bff1 100644
--- a/docs/templating.md
+++ b/docs/templating.md
@@ -67,6 +67,7 @@ Helmfile uses some OS environment variables to override default behaviour:
 * `HELMFILE_EXPERIMENTAL` - enable experimental features, expecting `true` lower case
 * `HELMFILE_ENVIRONMENT` - specify [Helmfile environment](environments.md), it has lower priority than CLI argument `--environment`
 * `HELMFILE_KUBE_CONTEXT` - specify the kubectl context, it has lower priority than CLI argument `--kube-context`
+* `HELMFILE_NAMESPACE` - specify the namespace, it has lower priority than CLI argument `--namespace`
 * `HELMFILE_TEMPDIR` - specify directory to store temporary files
 * `HELMFILE_UPGRADE_NOTICE_DISABLED` - expecting any non-empty value to skip the check for the latest version of Helmfile in [helmfile version](cli.md#version)
 * `HELMFILE_GO_YAML_V3` - use *go.yaml.in/yaml/v3* instead of *go.yaml.in/yaml/v2*.  It's `false` by default in Helmfile v0.x, and `true` in Helmfile v1.x.
diff --git a/pkg/config/global.go b/pkg/config/global.go
index 8811ff37..d96655a5 100644
--- a/pkg/config/global.go
+++ b/pkg/config/global.go
@@ -139,7 +139,17 @@ func (g *GlobalImpl) KubeContext() string {
 
 // Namespace returns the namespace to use.
 func (g *GlobalImpl) Namespace() string {
-	return g.GlobalOptions.Namespace
+	var namespace string
+
+	switch {
+	case g.GlobalOptions.Namespace != "":
+		namespace = g.GlobalOptions.Namespace
+	case os.Getenv("HELMFILE_NAMESPACE") != "":
+		namespace = os.Getenv("HELMFILE_NAMESPACE")
+	default:
+		namespace = ""
+	}
+	return namespace
 }
 
 // Chart returns the chart to use.
diff --git a/pkg/config/global_test.go b/pkg/config/global_test.go
index b77751dc..e5b91f4c 100644
--- a/pkg/config/global_test.go
+++ b/pkg/config/global_test.go
@@ -82,3 +82,40 @@ func TestKubeContext(t *testing.T) {
 	}
 	os.Unsetenv(envvar.KubeContext)
 }
+
+// TestNamespace tests the namespace flag and HELMFILE_NAMESPACE env var fallback
+func TestNamespace(t *testing.T) {
+	tests := []struct {
+		opts     GlobalOptions
+		env      string
+		expected string
+	}{
+		{
+			opts:     GlobalOptions{},
+			env:      "",
+			expected: "",
+		},
+		{
+			opts:     GlobalOptions{},
+			env:      "envset",
+			expected: "envset",
+		},
+		{
+			opts:     GlobalOptions{Namespace: "flagset"},
+			env:      "",
+			expected: "flagset",
+		},
+		{
+			opts:     GlobalOptions{Namespace: "flagset"},
+			env:      "envset",
+			expected: "flagset",
+		},
+	}
+
+	for _, test := range tests {
+		os.Setenv(envvar.Namespace, test.env)
+		received := NewGlobalImpl(&test.opts).Namespace()
+		require.Equalf(t, test.expected, received, "Namespace expected %s, received %s", test.expected, received)
+	}
+	os.Unsetenv(envvar.Namespace)
+}
diff --git a/pkg/envvar/const.go b/pkg/envvar/const.go
index f220e505..d6f1575f 100644
--- a/pkg/envvar/const.go
+++ b/pkg/envvar/const.go
@@ -10,6 +10,7 @@ const (
 	Experimental          = "HELMFILE_EXPERIMENTAL" // environment variable for experimental features, expecting "true" lower case
 	Environment           = "HELMFILE_ENVIRONMENT"
 	KubeContext           = "HELMFILE_KUBE_CONTEXT"
+	Namespace             = "HELMFILE_NAMESPACE"
 	FilePath              = "HELMFILE_FILE_PATH"
 	TempDir               = "HELMFILE_TEMPDIR"
 	UpgradeNoticeDisabled = "HELMFILE_UPGRADE_NOTICE_DISABLED"