diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8ecdc3fc..1e47ebeb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,11 +2,12 @@
 
 ## master / unreleased
 
+* [BUGFIX] Add support the `local` ruler client type
 * [CHANGE] The project is now licensed with Apache-2.0 license. #169
 * [CHANGE] Add overrides config to tsdb store-gateway. #167
 * [CHANGE] Ingesters now default to running as `StatefulSet` with WAL enabled. It is controlled by the config `$._config.ingester_deployment_without_wal` which is `false` by default. Setting the config to `true` will yeild the old behaviour (stateless `Deployment` without WAL enabled). #72
 * [CHANGE] We now allow queries that are 32 days long. For example, rate(metric[32d]). Before it was 31d. #173
-* [BUGFIX] Add support the `local` ruler client type
+* [ENHANCEMENT] Enable support for HA in the Cortex Alertmanager #147
 
 ## 1.3.0 / 2020-08-21
 
diff --git a/cortex/alertmanager.libsonnet b/cortex/alertmanager.libsonnet
index e5bb15d8..61d04f5b 100644
--- a/cortex/alertmanager.libsonnet
+++ b/cortex/alertmanager.libsonnet
@@ -4,15 +4,23 @@
   local container = $.core.v1.container,
   local statefulSet = $.apps.v1.statefulSet,
   local service = $.core.v1.service,
+  local isHA = $._config.alertmanager.replicas > 1,
+  local peers = if isHA then
+    [
+      'alertmanager-%d.alertmanager.%s.svc.%s.local:%s' % [i, $._config.namespace, $._config.cluster, $._config.alertmanager.gossip_port]
+      for i in std.range(0, $._config.alertmanager.replicas - 1)
+    ]
+  else [],
 
   alertmanager_args::
     {
       target: 'alertmanager',
       'log.level': 'debug',
 
+      'experimental.alertmanager.enable-api': 'true',
       'alertmanager.storage.type': 'gcs',
       'alertmanager.storage.path': '/data',
-      'alertmanager.gcs.bucketname': '%(cluster)s-cortex-configdb-%(namespace)s' % $._config,
+      'alertmanager.storage.gcs.bucketname': '%(cluster)s-cortex-%(namespace)s' % $._config,
       'alertmanager.web.external-url': '%s/alertmanager' % $._config.external_url,
     },
 
@@ -27,8 +35,22 @@
   alertmanager_container::
     if $._config.alertmanager_enabled then
       container.new('alertmanager', $._images.alertmanager) +
-      container.withPorts($.util.defaultPorts) +
-      container.withArgsMixin($.util.mapToFlags($.alertmanager_args)) +
+      container.withPorts(
+        $.util.defaultPorts +
+        if isHA then [
+          $.core.v1.containerPort.newUDP('gossip-udp', $._config.alertmanager.gossip_port),
+          $.core.v1.containerPort.new('gossip-tcp', $._config.alertmanager.gossip_port),
+        ]
+        else [],
+      ) +
+      container.withEnvMixin([container.envType.fromFieldPath('POD_IP', 'status.podIP')]) +
+      container.withArgsMixin(
+        $.util.mapToFlags($.alertmanager_args) +
+        if isHA then
+          ['--cluster.listen-address=[$(POD_IP)]:%s' % $._config.alertmanager_gossip_port] +
+          ['--cluster.peer=%s' % peer for peer in peers]
+        else [],
+      ) +
       container.withVolumeMountsMixin([volumeMount.new('alertmanager-data', '/data')]) +
       $.util.resourcesRequests('100m', '1Gi') +
       $.util.readinessProbe +
@@ -37,7 +59,7 @@
 
   alertmanager_statefulset:
     if $._config.alertmanager_enabled then
-      statefulSet.new('alertmanager', 1, [$.alertmanager_container], $.alertmanager_pvc) +
+      statefulSet.new('alertmanager', $._config.alertmanager.replicas, [$.alertmanager_container], $.alertmanager_pvc) +
       statefulSet.mixin.spec.withServiceName('alertmanager') +
       statefulSet.mixin.metadata.withNamespace($._config.namespace) +
       statefulSet.mixin.metadata.withLabels({ name: 'alertmanager' }) +
@@ -50,6 +72,10 @@
 
   alertmanager_service:
     if $._config.alertmanager_enabled then
-      $.util.serviceFor($.alertmanager_statefulset)
+      if isHA then
+        $.util.serviceFor($.alertmanager_statefulset) +
+        service.mixin.spec.withClusterIp('None')
+      else
+        $.util.serviceFor($.alertmanager_statefulset)
     else {},
 }
diff --git a/cortex/config.libsonnet b/cortex/config.libsonnet
index d359f22f..35cc73d4 100644
--- a/cortex/config.libsonnet
+++ b/cortex/config.libsonnet
@@ -243,6 +243,11 @@
         },
       }[$._config.ruler_client_type],
 
+    alertmanager: {
+      replicas: 3,
+      gossip_port: 9094,
+    },
+
     overrides: {
       // === Per-tenant usage limits. ===
       //
diff --git a/cortex/images.libsonnet b/cortex/images.libsonnet
index a4be104a..14bc4781 100644
--- a/cortex/images.libsonnet
+++ b/cortex/images.libsonnet
@@ -5,8 +5,9 @@
     memcachedExporter: 'prom/memcached-exporter:v0.6.0',
 
     // Our services.
-    cortex: 'cortexproject/cortex:v1.2.0',
+    cortex: 'cortexproject/cortex:v1.3.0',
 
+    alertmanager: self.cortex,
     distributor: self.cortex,
     ingester: self.cortex,
     querier: self.cortex,
@@ -18,8 +19,6 @@
     store_gateway: self.cortex,
 
     query_tee: 'quay.io/cortexproject/query-tee:master-5d7b05c3',
-    // TODO(gouthamve/jtlisi): Upstream the ruler and AM configs.
-    alertmanager: 'jtlisi/cortex:20190819_alertmanager_update-faa66aa43',
     testExporter: 'cortexproject/test-exporter:master-be013707',
   },
 }