diff --git a/schemas/browserlib/extract-cssdfn.json b/schemas/browserlib/extract-cssdfn.json
index 0de91ef3..f619f7c1 100644
--- a/schemas/browserlib/extract-cssdfn.json
+++ b/schemas/browserlib/extract-cssdfn.json
@@ -18,6 +18,7 @@
           "value": { "$ref": "../common.json#/$defs/cssValue" },
           "newValues": { "$ref": "../common.json#/$defs/cssValue" },
           "values": { "$ref": "../common.json#/$defs/cssValues" },
+          "legacyAliasOf": { "$ref": "../common.json#/$defs/cssPropertyName" },
           "styleDeclaration": {
             "type": "array",
             "items": { "type": "string" },
diff --git a/src/browserlib/extract-cssdfn.mjs b/src/browserlib/extract-cssdfn.mjs
index 89d7c5af..12f25d4d 100644
--- a/src/browserlib/extract-cssdfn.mjs
+++ b/src/browserlib/extract-cssdfn.mjs
@@ -18,13 +18,17 @@ export default function () {
   const warnings = [];
 
   const res = {
-    // Properties are always defined in dedicated tables in modern CSS specs
-    properties: extractDfns({
-      selector: 'table.propdef:not(.attrdef)',
-      extractor: extractTableDfns,
-      duplicates: 'merge',
-      warnings
-    }),
+    // Properties are always defined in dedicated tables in modern CSS specs,
+    // Legacy properties are always defined in prose in a dfn with a nearby
+    // reference to "legacy name alias"
+    properties: []
+      .concat(extractDfns({
+        selector: 'table.propdef:not(.attrdef)',
+        extractor: extractTableDfns,
+        duplicates: 'merge',
+        warnings
+      }))
+      .concat(extractLegacyProperties(document)),
 
     // At-rules, selectors, functions and types are defined through dfns with
     // the right "data-dfn-type" attribute
@@ -826,3 +830,56 @@ const extractProductionRules = root => {
 
   return rules;
 }
+
+
+/**
+ * Extract legacy alias relationships, looking for occurrences of the term
+ * "legacy name alias".
+ *
+ * Next to it, there should be:
+ * 1. a dfn for a property followed by a reference to the aliased property; or
+ * 2. a table with two columns: dfns in the first column, references to the
+ * aliased properties in the second column.
+ */
+const extractLegacyProperties = doc =>
+  [...doc.querySelectorAll('a[href*="#legacy-name-alias"]')]
+    .map(el => el.parentElement)
+    .map(el => {
+      const dfn = el.querySelector('dfn[data-dfn-type="property"]');
+      const alias = el.querySelector('a[data-link-type="property"]');
+      if (dfn && alias) {
+        // Aliasing is defined in prose
+        return {
+          name: normalize(dfn.textContent),
+          href: getAbsoluteUrl(dfn),
+          legacyAliasOf: normalize(alias.textContent)
+        };
+      }
+      else {
+        // Look for a compat table right after the paragraph
+        const table = el.nextElementSibling;
+        if (!table || table.nodeName !== 'TABLE') {
+          return null;
+        }
+        if ([...table.querySelectorAll('thead > tr > th')].length !== 2) {
+          return null;
+        }
+        return [...table.querySelectorAll('tbody > tr')]
+          .map(row => {
+            const dfn = row.querySelector('dfn[data-dfn-type="property"]');
+            const alias = row.querySelector('a[data-link-type="property"]');
+            if (dfn && alias) {
+              return {
+                name: normalize(dfn.textContent),
+                href: getAbsoluteUrl(dfn),
+                legacyAliasOf: normalize(alias.textContent)
+              };
+            }
+            else {
+              return null;
+            }
+          });
+      }
+    })
+    .flat()
+    .filter(prop => !!prop);
diff --git a/tests/extract-css.js b/tests/extract-css.js
index 9faa156d..4d57ed12 100644
--- a/tests/extract-css.js
+++ b/tests/extract-css.js
@@ -1580,6 +1580,69 @@ that spans multiple lines */
       "value": "currentColor | <color> [<icccolor>] | inherit",
       "initial": "white"
    }]
+  },
+
+  {
+    title: 'extracts a legacy name alias',
+    html: `<p>
+      The <dfn data-dfn-type="property" id="old">good-old</dfn>
+      property is a <a href="blah#legacy-name-alias">legacy name alias</a> of
+      the <a data-link-type="property">brand-new</a> property.
+    </p>
+    `,
+    css: [{
+      name: 'good-old',
+      href: 'about:blank#old',
+      legacyAliasOf: 'brand-new'
+    }]
+  },
+
+  {
+    title: 'extracts legacy name aliases from a suitable table',
+    html: `<p>
+      The following properties must be supported as
+      <a href="foo#legacy-name-alias">legacy name aliases</a> of the
+      corresponding unprefixed property:
+    </p>
+    <table>
+      <thead>
+        <tr><th>First column</th><th>Second column</th></tr>
+      </thead>
+      <tbody>
+        <tr>
+          <td><dfn data-dfn-type="property" id="old">good-old</dfn></td>
+          <td><a data-link-type="property">brand-new</a></td>
+        </tr>
+        <tr>
+          <td><dfn data-dfn-type="property" id="webkit">-webkit-old</dfn></td>
+          <td><a data-link-type="property">brand-new</a></td>
+        </tr>
+      </tbody>
+    </table>
+    `,
+    css: [
+      {
+        name: 'good-old',
+        href: 'about:blank#old',
+        legacyAliasOf: 'brand-new'
+      },
+      {
+        name: '-webkit-old',
+        href: 'about:blank#webkit',
+        legacyAliasOf: 'brand-new'
+      }
+    ]
+  },
+
+  {
+    title: 'avoids legacy name alias references in prose without a dfn',
+    html: `<p>
+      The <a data-link-type="property" id="old">good-old</a>
+      property is a <a href="blah#legacy-name-alias">legacy name alias</a> of
+      the <a data-link-type="property">brand-new</a> property.
+    </p>
+    `,
+    css: []
   }
 ];