diff --git a/packages/alfa-rules/src/rules.ts b/packages/alfa-rules/src/rules.ts
index 19730e49b7..d0bb8580fe 100644
--- a/packages/alfa-rules/src/rules.ts
+++ b/packages/alfa-rules/src/rules.ts
@@ -49,6 +49,7 @@ export { default as R48 } from "./sia-r48/rule";
 export { default as R49 } from "./sia-r49/rule";
 export { default as R50 } from "./sia-r50/rule";
 export { default as R53 } from "./sia-r53/rule";
+export { default as R54 } from "./sia-r54/rule";
 export { default as R55 } from "./sia-r55/rule";
 export { default as R56 } from "./sia-r56/rule";
 export { default as R57 } from "./sia-r57/rule";
diff --git a/packages/alfa-rules/src/sia-r54/rule.ts b/packages/alfa-rules/src/sia-r54/rule.ts
new file mode 100644
index 0000000000..6f9976947e
--- /dev/null
+++ b/packages/alfa-rules/src/sia-r54/rule.ts
@@ -0,0 +1,54 @@
+import { Rule, Diagnostic } from "@siteimprove/alfa-act";
+import { Node } from "@siteimprove/alfa-aria";
+import { Element } from "@siteimprove/alfa-dom";
+import { Predicate } from "@siteimprove/alfa-predicate";
+import { Err, Ok } from "@siteimprove/alfa-result";
+import { Page } from "@siteimprove/alfa-web";
+
+import { isIgnored } from "../common/predicate";
+import { expectation } from "../common/expectation";
+
+const { and, not } = Predicate;
+const { isElement } = Element;
+
+export default Rule.Atomic.of<Page, Element>({
+  uri: "https://alfa.siteimprove.com/rules/sia-r54",
+  evaluate({ device, document }) {
+    return {
+      applicability() {
+        return document
+          .descendants({ flattened: true, nested: true })
+          .filter(isElement)
+          .filter(
+            and(not(isIgnored(device)), (element) =>
+              Node.from(element, device)
+                .attribute("aria-live")
+                .some((attribute) => attribute.value === "assertive")
+            )
+          );
+      },
+
+      expectations(target) {
+        return {
+          1: expectation(
+            Node.from(target, device)
+              .attribute("aria-atomic")
+              .some((attribute) => attribute.value === "true"),
+            () => Outcomes.IsAtomic,
+            () => Outcomes.IsNotAtomic
+          ),
+        };
+      },
+    };
+  },
+});
+
+export namespace Outcomes {
+  export const IsAtomic = Ok.of(
+    Diagnostic.of("The assertive region is atomic")
+  );
+
+  export const IsNotAtomic = Err.of(
+    Diagnostic.of("The assertive region is not atomic")
+  );
+}
diff --git a/packages/alfa-rules/test/sia-r54/rule.spec.tsx b/packages/alfa-rules/test/sia-r54/rule.spec.tsx
new file mode 100644
index 0000000000..952215a25e
--- /dev/null
+++ b/packages/alfa-rules/test/sia-r54/rule.spec.tsx
@@ -0,0 +1,72 @@
+import { test } from "@siteimprove/alfa-test";
+
+import { h } from "@siteimprove/alfa-dom";
+
+import R54, { Outcomes } from "../../src/sia-r54/rule";
+
+import { evaluate } from "../common/evaluate";
+import { passed, failed, inapplicable } from "../common/outcome";
+
+test("evaluate() passes an assertive and atomic element", async (t) => {
+  const target = (
+    <div aria-live="assertive" aria-atomic="true">
+      Some words
+    </div>
+  );
+
+  const document = h.document([target]);
+
+  t.deepEqual(await evaluate(R54, { document }), [
+    passed(R54, target, {
+      1: Outcomes.IsAtomic,
+    }),
+  ]);
+});
+
+test("evaluate() fails an element which is assertive but not atomic", async (t) => {
+  const target = <div aria-live="assertive"> Some words </div>;
+
+  const document = h.document([target]);
+
+  t.deepEqual(await evaluate(R54, { document }), [
+    failed(R54, target, {
+      1: Outcomes.IsNotAtomic,
+    }),
+  ]);
+});
+
+test("evaluate() fails an assertive element with an incorrect aria-atomic attribute", async (t) => {
+  const target = (
+    <div aria-live="assertive" aria-atomic="wrong">
+      Some words
+    </div>
+  );
+
+  const document = h.document([target]);
+
+  t.deepEqual(await evaluate(R54, { document }), [
+    failed(R54, target, {
+      1: Outcomes.IsNotAtomic,
+    }),
+  ]);
+});
+
+test("evaluate() is inapplicable to elements that are not in the accessibility tree", async (t) => {
+  const target = (
+    <div hidden aria-live="assertive" aria-atomic="true">
+      Some words
+    </div>
+  );
+
+  const document = h.document([target]);
+
+  t.deepEqual(await evaluate(R54, { document }), [inapplicable(R54)]);
+});
+
+test("evaluate() is inapplicable to an element which is not assertive", async (t) => {
+  const target = <div>Some words</div>;
+
+  const document = h.document([target]);
+
+  t.deepEqual(await evaluate(R54, { document }), [inapplicable(R54)]);
+});
diff --git a/packages/alfa-rules/tsconfig.json b/packages/alfa-rules/tsconfig.json
index 49a1867d77..3021cde04d 100644
--- a/packages/alfa-rules/tsconfig.json
+++ b/packages/alfa-rules/tsconfig.json
@@ -113,6 +113,7 @@
     "src/sia-r5/rule.ts",
     "src/sia-r50/rule.ts",
     "src/sia-r53/rule.ts",
+    "src/sia-r54/rule.ts",
     "src/sia-r55/rule.ts",
     "src/sia-r56/rule.ts",
     "src/sia-r57/rule.ts",
@@ -185,6 +186,7 @@
     "test/sia-r45/rule.spec.tsx",
     "test/sia-r46/rule.spec.tsx",
     "test/sia-r53/rule.spec.tsx",
+    "test/sia-r54/rule.spec.tsx",
     "test/sia-r55/rule.spec.tsx",
     "test/sia-r56/rule.spec.tsx",
     "test/sia-r57/rule.spec.tsx",