diff --git a/etc/kayobe/kolla/config/prometheus/rabbitmq.rules b/etc/kayobe/kolla/config/prometheus/rabbitmq.rules
index d72230421..82022d72a 100644
--- a/etc/kayobe/kolla/config/prometheus/rabbitmq.rules
+++ b/etc/kayobe/kolla/config/prometheus/rabbitmq.rules
@@ -6,7 +6,7 @@ groups:
 - name: rabbitmq.rules
   rules:
   - alert: RabbitMQNodeDown
-    expr: sum(rabbitmq_build_info{instance!=""}) < 3
+    expr: sum(rabbitmq_build_info{instance!=""}) < {% endraw %}{{ alertmanager_number_of_rabbitmq_nodes }}{% raw %}
     for: 30m
     labels:
       severity: critical
diff --git a/etc/kayobe/stackhpc-monitoring.yml b/etc/kayobe/stackhpc-monitoring.yml
index 5eee4b19c..2b34c5566 100644
--- a/etc/kayobe/stackhpc-monitoring.yml
+++ b/etc/kayobe/stackhpc-monitoring.yml
@@ -26,6 +26,9 @@ alertmanager_packet_drop_threshold: 1
 # packets/s averaged over 5 minutes.
 alertmanager_packet_errors_threshold: 1
 
+# Number of RabbitMQ nodes in the cluster.
+alertmanager_number_of_rabbitmq_nodes: "{{ groups['controllers'] | length }}"
+
 ###############################################################################
 # Exporter configuration
 
diff --git a/releasenotes/notes/use-length-for-rabbitmq-node-down-rule-c9e9c6b09f57954d.yaml b/releasenotes/notes/use-length-for-rabbitmq-node-down-rule-c9e9c6b09f57954d.yaml
new file mode 100644
index 000000000..e7b7b2f9a
--- /dev/null
+++ b/releasenotes/notes/use-length-for-rabbitmq-node-down-rule-c9e9c6b09f57954d.yaml
@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    Allow for easy customisation of the number of expected `RabbitMQ`
+    nodes when evaluating the alert `RabbitMQNodeDown`. It is set by
+    the `alertmanager_number_of_rabbitmq_nodes` which defaults to the
+    number of `controllers`. This is benefical for deployments that
+    do not use a standard three node setup.