diff --git a/content/en/docs/concepts/services-networking/service.md b/content/en/docs/concepts/services-networking/service.md
index fbecdb3316..c215a2fd76 100644
--- a/content/en/docs/concepts/services-networking/service.md
+++ b/content/en/docs/concepts/services-networking/service.md
@@ -202,6 +202,17 @@ endpoints.
 EndpointSlices provide additional attributes and functionality which is
 described in detail in [EndpointSlices](/docs/concepts/services-networking/endpoint-slices/).
 
+### Application protocol
+
+{{< feature-state for_k8s_version="v1.18" state="alpha" >}}
+
+The AppProtocol field provides a way to specify an application protocol to be
+used for each Service port.
+
+As an alpha feature, this field is not enabled by default. To use this field,
+enable the `ServiceAppProtocol` [feature
+gate](/docs/reference/command-line-tools-reference/feature-gates/).
+
 ## Virtual IPs and service proxies
 
 Every node in a Kubernetes cluster runs a `kube-proxy`. `kube-proxy` is
diff --git a/content/en/docs/reference/command-line-tools-reference/feature-gates.md b/content/en/docs/reference/command-line-tools-reference/feature-gates.md
index d284df9e5f..073c9344e4 100644
--- a/content/en/docs/reference/command-line-tools-reference/feature-gates.md
+++ b/content/en/docs/reference/command-line-tools-reference/feature-gates.md
@@ -124,6 +124,7 @@ different Kubernetes components.
 | `RuntimeClass` | `false` | Alpha | 1.12 | 1.13 |
 | `RuntimeClass` | `true` | Beta | 1.14 | |
 | `SCTPSupport` | `false` | Alpha | 1.12 | |
+| `ServiceAppProtocol` | `false` | Alpha | 1.18 | |
 | `ServerSideApply` | `false` | Alpha | 1.14 | 1.15 |
 | `ServerSideApply` | `true` | Beta | 1.16 | |
 | `ServiceNodeExclusion` | `false` | Alpha | 1.8 | |
@@ -458,6 +459,7 @@ Each feature gate is designed for enabling/disabling a specific feature:
 - `ScheduleDaemonSetPods`: Enable DaemonSet Pods to be scheduled by the default scheduler instead of the DaemonSet controller.
 - `SCTPSupport`: Enables the usage of SCTP as `protocol` value in `Service`, `Endpoint`, `NetworkPolicy` and `Pod` definitions
 - `ServerSideApply`: Enables the [Sever Side Apply (SSA)](/docs/reference/using-api/api-concepts/#server-side-apply) path at the API Server.
+- `ServiceAppProtocol`: Enables the `AppProtocol` field on Services and Endpoints.
 - `ServiceLoadBalancerFinalizer`: Enable finalizer protection for Service load balancers.
 - `ServiceNodeExclusion`: Enable the exclusion of nodes from load balancers created by a cloud provider.
   A node is eligible for exclusion if labelled with "`alpha.service-controller.kubernetes.io/exclude-balancer`" key or `node.kubernetes.io/exclude-from-external-load-balancers`.