diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1997ed853e2a..16bb0fb7edf6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## Main
 
+* [6136](https://github.com/grafana/loki/pull/6136) **periklis**: Add support for alertmanager header authorization
 * [6102](https://github.com/grafana/loki/pull/6102) **timchenko-a**: Add multi-tenancy support to lambda-promtail
 * [5971](https://github.com/grafana/loki/pull/5971) **kavirajk**: Record statistics about metadata queries such as labels and series queries in `metrics.go` as well
 * [5790](https://github.com/grafana/loki/pull/5790) **chaudum**: Add UDP support for Promtail's syslog target.
diff --git a/docs/sources/configuration/_index.md b/docs/sources/configuration/_index.md
index 05d29f5e1f44..b91b3f7be1b2 100644
--- a/docs/sources/configuration/_index.md
+++ b/docs/sources/configuration/_index.md
@@ -636,6 +636,26 @@ wal_cleaner:
 # CLI flag: -ruler.alertmanager-url
 [alertmanager_url: <string> | default = ""]
 
+
+alertmanager_client:
+  # Sets the `Authorization` header on every remote write request with the
+  # configured username and password.
+  # password and password_file are mutually exclusive.
+  basic_auth:
+    [username: <string>]
+    [password: <secret>]
+
+  # Optional `Authorization` header configuration.
+  authorization:
+    # Sets the authentication type.
+    [type: <string> | default: Bearer]
+    # Sets the credentials. It is mutually exclusive with
+    # `credentials_file`.
+    [credentials: <secret>]
+    # Sets the credentials to the credentials read from the configured file.
+    # It is mutually exclusive with `credentials`.
+    [credentials_file: <filename>]
+
 # Use DNS SRV records to discover Alertmanager hosts.
 # CLI flag: -ruler.alertmanager-discovery
 [enable_alertmanager_discovery: <boolean> | default = false]
diff --git a/pkg/ruler/base/notifier.go b/pkg/ruler/base/notifier.go
index 648d5dbb0a44..d9b28bfa8547 100644
--- a/pkg/ruler/base/notifier.go
+++ b/pkg/ruler/base/notifier.go
@@ -23,13 +23,15 @@ import (
 )
 
 type NotifierConfig struct {
-	TLS       tls.ClientConfig `yaml:",inline"`
-	BasicAuth util.BasicAuth   `yaml:",inline"`
+	TLS        tls.ClientConfig `yaml:",inline"`
+	BasicAuth  util.BasicAuth   `yaml:",inline"`
+	HeaderAuth util.HeaderAuth  `yaml:",inline"`
 }
 
 func (cfg *NotifierConfig) RegisterFlags(f *flag.FlagSet) {
 	cfg.TLS.RegisterFlagsWithPrefix("ruler.alertmanager-client", f)
 	cfg.BasicAuth.RegisterFlagsWithPrefix("ruler.alertmanager-client.", f)
+	cfg.HeaderAuth.RegisterFlagsWithPrefix("ruler.alertmanager-client.", f)
 }
 
 // rulerNotifier bundles a notifier.Manager together with an associated
@@ -197,5 +199,20 @@ func amConfigFromURL(rulerConfig *Config, url *url.URL, apiVersion config.Alertm
 		}
 	}
 
+	if rulerConfig.Notifier.HeaderAuth.IsEnabled() {
+		if rulerConfig.Notifier.HeaderAuth.Credentials != "" {
+			amConfig.HTTPClientConfig.Authorization = &config_util.Authorization{
+				Type:        rulerConfig.Notifier.HeaderAuth.Type,
+				Credentials: config_util.Secret(rulerConfig.Notifier.HeaderAuth.Credentials),
+			}
+		} else if rulerConfig.Notifier.HeaderAuth.CredentialsFile != "" {
+			amConfig.HTTPClientConfig.Authorization = &config_util.Authorization{
+				Type:            rulerConfig.Notifier.HeaderAuth.Type,
+				CredentialsFile: rulerConfig.Notifier.HeaderAuth.CredentialsFile,
+			}
+
+		}
+	}
+
 	return amConfig
 }
diff --git a/pkg/ruler/base/notifier_test.go b/pkg/ruler/base/notifier_test.go
index 1f5b7776b780..eb8959e8b90e 100644
--- a/pkg/ruler/base/notifier_test.go
+++ b/pkg/ruler/base/notifier_test.go
@@ -221,6 +221,78 @@ func TestBuildNotifierConfig(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "with Header Authorization",
+			cfg: &Config{
+				AlertmanagerURL: "http://alertmanager-0.default.svc.cluster.local/alertmanager",
+				Notifier: NotifierConfig{
+					HeaderAuth: util.HeaderAuth{
+						Type:        "Bearer",
+						Credentials: "jacob",
+					},
+				},
+			},
+			ncfg: &config.Config{
+				AlertingConfig: config.AlertingConfig{
+					AlertmanagerConfigs: []*config.AlertmanagerConfig{
+						{
+							HTTPClientConfig: config_util.HTTPClientConfig{
+								Authorization: &config_util.Authorization{
+									Type:        "Bearer",
+									Credentials: config_util.Secret("jacob"),
+								},
+							},
+							APIVersion: "v1",
+							Scheme:     "http",
+							PathPrefix: "/alertmanager",
+							ServiceDiscoveryConfigs: discovery.Configs{
+								discovery.StaticConfig{
+									{
+										Targets: []model.LabelSet{{"__address__": "alertmanager-0.default.svc.cluster.local"}},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "with Header Authorization and credentials file",
+			cfg: &Config{
+				AlertmanagerURL: "http://alertmanager-0.default.svc.cluster.local/alertmanager",
+				Notifier: NotifierConfig{
+					HeaderAuth: util.HeaderAuth{
+						Type:            "Bearer",
+						CredentialsFile: "/path/to/secret/file",
+					},
+				},
+			},
+			ncfg: &config.Config{
+				AlertingConfig: config.AlertingConfig{
+					AlertmanagerConfigs: []*config.AlertmanagerConfig{
+						{
+							HTTPClientConfig: config_util.HTTPClientConfig{
+								Authorization: &config_util.Authorization{
+									Type:            "Bearer",
+									CredentialsFile: "/path/to/secret/file",
+								},
+							},
+							APIVersion: "v1",
+							Scheme:     "http",
+							PathPrefix: "/alertmanager",
+							ServiceDiscoveryConfigs: discovery.Configs{
+								discovery.StaticConfig{
+									{
+										Targets: []model.LabelSet{{"__address__": "alertmanager-0.default.svc.cluster.local"}},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name: "with external labels",
 			cfg: &Config{
diff --git a/pkg/util/http.go b/pkg/util/http.go
index 45f8da374186..3305a9410a49 100644
--- a/pkg/util/http.go
+++ b/pkg/util/http.go
@@ -43,6 +43,24 @@ func (b BasicAuth) IsEnabled() bool {
 	return b.Username != "" || b.Password != ""
 }
 
+// HeaderAuth condigures header based authorization for HTTP clients.
+type HeaderAuth struct {
+	Type            string `yaml:"type,omitempty"`
+	Credentials     string `yaml:"credentials,omitempty"`
+	CredentialsFile string `yaml:"credentials_file,omitempty"`
+}
+
+func (h *HeaderAuth) RegisterFlagsWithPrefix(prefix string, f *flag.FlagSet) {
+	f.StringVar(&h.Type, prefix+"type", "Bearer", "HTTP Header authorization type (default: Bearer).")
+	f.StringVar(&h.Credentials, prefix+"credentials", "", "HTTP Header authorization credentials.")
+	f.StringVar(&h.CredentialsFile, prefix+"credentials-file", "", "HTTP Header authorization credentials file.")
+}
+
+// IsEnabled returns false if header authorization isn't enabled.
+func (h HeaderAuth) IsEnabled() bool {
+	return h.Credentials != "" || h.CredentialsFile != ""
+}
+
 // WriteJSONResponse writes some JSON as a HTTP response.
 func WriteJSONResponse(w http.ResponseWriter, v interface{}) {
 	w.Header().Set("Content-Type", "application/json")