diff --git a/defaults/main.yml b/defaults/main.yml
index bb774e2..5d94b3c 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -34,6 +34,8 @@ alertmanager_web_tls_key_source: mykey.pem
 
 alertmanager_log_level: error
 
+alertmanager_storage_retention: 120h
+
 alertmanager_template_files:
   - alertmanager/templates/*.tmpl
 
diff --git a/templates/etc/systemd/system/alertmanager.service.j2 b/templates/etc/systemd/system/alertmanager.service.j2
index 9e81c8e..b65c0ad 100644
--- a/templates/etc/systemd/system/alertmanager.service.j2
+++ b/templates/etc/systemd/system/alertmanager.service.j2
@@ -14,6 +14,7 @@ WorkingDirectory={{ alertmanager_base_dir }}
 ExecReload=/bin/kill -HUP $MAINPID
 ExecStart={{ alertmanager_base_dir }}/alertmanager \
   --storage.path={{ alertmanager_data_dir }} \
+  --data.retention={{ alertmanager_storage_retention }} \
   --web.config.file={{ alertmanager_config_dir }}/web.yml \
   --web.listen-address={{ alertmanager_web_bind_ip }}:{{ alertmanager_web_bind_port }} \
   --web.external-url={{ alertmanager_web_external_url }} \