diff --git a/packages/dom/src/css.ts b/packages/dom/src/css.ts
index 6882b1e..b2b70c6 100644
--- a/packages/dom/src/css.ts
+++ b/packages/dom/src/css.ts
@@ -21,6 +21,7 @@
 import optimalSelect from 'optimal-select';
 import type { CssSelector, Matcher } from '@apache-annotator/selector';
 import { ownerDocument } from './owner-document';
+import { toRange } from './range-node-conversion';
 
 /**
  * Find the elements corresponding to the given {@link
@@ -45,16 +46,17 @@
  * > “If […] the user agent discovers multiple matching text sequences, then the
  * > selection SHOULD be treated as matching all of the matches.”
  *
- * @param selector - The {@link CssSelector} to be anchored
- * @returns A {@link Matcher} function that applies `selector` to a given {@link https://developer.mozilla.org/en-US/docs/Web/API/Range
- * | Range}
+ * @param selector - The {@link CssSelector} to be anchored.
+ * @returns A {@link Matcher} function that applies `selector` to a given
+ * `scope`.
  *
  * @public
  */
 export function createCssSelectorMatcher(
   selector: CssSelector,
-): Matcher<Range, Element> {
+): Matcher<Node | Range, Element> {
   return async function* matchAll(scope) {
+    scope = toRange(scope);
     const document = ownerDocument(scope);
     for (const element of document.querySelectorAll(selector.value)) {
       const range = document.createRange();
diff --git a/packages/dom/src/owner-document.ts b/packages/dom/src/owner-document.ts
index 1c0621e..fe7818a 100644
--- a/packages/dom/src/owner-document.ts
+++ b/packages/dom/src/owner-document.ts
@@ -18,8 +18,19 @@
  * under the License.
  */
 
-export function ownerDocument(range: Range): Document {
-  const { startContainer } = range;
+/**
+ * Get the ownerDocument for either a range or a node.
+ *
+ * @param nodeOrRange the node or range for which to get the owner document.
+ */
+export function ownerDocument(nodeOrRange: Node | Range): Document {
+  const node = isRange(nodeOrRange)
+    ? nodeOrRange.startContainer
+    : nodeOrRange;
   // node.ownerDocument is null iff node is itself a Document.
-  return startContainer.ownerDocument ?? (startContainer as Document);
+  return node.ownerDocument ?? (node as Document);
+}
+
+function isRange(nodeOrRange: Node | Range): nodeOrRange is Range {
+  return ('startContainer' in nodeOrRange);
 }
diff --git a/packages/dom/src/range-node-conversion.ts b/packages/dom/src/range-node-conversion.ts
new file mode 100644
index 0000000..fd62543
--- /dev/null
+++ b/packages/dom/src/range-node-conversion.ts
@@ -0,0 +1,45 @@
+/**
+ * @license
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { ownerDocument } from "./owner-document";
+
+/**
+ * Returns a range that exactly selects the contents of the given node.
+ *
+ * This function is idempotent: If the given argument is already a range, it
+ * simply returns that range.
+ *
+ * @param nodeOrRange The node/range to convert to a range if it is not already
+ * a range.
+ */
+export function toRange(nodeOrRange: Node | Range): Range {
+  if (isRange(nodeOrRange)) {
+    return nodeOrRange;
+  } else {
+    const node = nodeOrRange;
+    const range = ownerDocument(node).createRange();
+    range.selectNodeContents(node);
+    return range;
+  }
+}
+
+function isRange(nodeOrRange: Node | Range): nodeOrRange is Range {
+  return ('startContainer' in nodeOrRange);
+}