diff --git a/src/index.js b/src/index.js
index 8c22d820..25c285e6 100644
--- a/src/index.js
+++ b/src/index.js
@@ -146,12 +146,30 @@ function ncc (
     }
   });
 
-  const externalMap = new Map();
+  const externalMap = (() => {
+    const regexps = [];
+    const aliasMap = new Map();
+
+    function set(key, value) {
+      if (key instanceof RegExp)
+        regexps.push(key);
+      aliasMap.set(key, value);
+    }
+
+    function get(key) {
+      if (aliasMap.has(key)) return aliasMap.get(key);
+
+      const matchedRegex = regexps.find(regex => regex.test(key));
+      return matchedRegex !== null ? aliasMap.get(matchedRegex) : null;
+    }
+
+    return { get, set };
+  })();
 
   if (Array.isArray(externals))
     externals.forEach(external => externalMap.set(external, external));
   else if (typeof externals === 'object')
-    Object.keys(externals).forEach(external => externalMap.set(external, externals[external]));
+    Object.keys(externals).forEach(external => externalMap.set(external[0] === '/' && external[external.length - 1] === '/' ? new RegExp(external.slice(1, -1)) : external, externals[external]));
 
   let watcher, watchHandler, rebuildHandler;
 
@@ -260,8 +278,9 @@ function ncc (
     },
     // https://github.com/vercel/ncc/pull/29#pullrequestreview-177152175
     node: false,
-    externals: ({ context, request }, callback) => {
-      if (externalMap.has(request)) return callback(null, `commonjs ${externalMap.get(request)}`);
+    externals ({ context, request }, callback) {
+      const external = externalMap.get(request);
+      if (external) return callback(null, `commonjs ${external}`);
       return callback();
     },
     module: {
diff --git a/test/index.test.js b/test/index.test.js
index 84d91716..ea31bd9f 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -42,7 +42,8 @@ for (const unitTest of fs.readdirSync(`${__dirname}/unit`)) {
       },
       externals: {
         'piscina': 'piscina',
-        'externaltest': 'externalmapped'
+        'externaltest': 'externalmapped',
+        '/\\w+-regex/': 'regexexternal',
       }
     }, opts)).then(
       async ({ code, assets, map }) => {
diff --git a/test/unit/externals/input.js b/test/unit/externals/input.js
index 794456be..22b98b25 100644
--- a/test/unit/externals/input.js
+++ b/test/unit/externals/input.js
@@ -1,3 +1,6 @@
 const external = require('externaltest');
+const regexpExternal = require('external-regex');
 
 console.log(external);
+console.log(regexpExternal);
+
diff --git a/test/unit/externals/output-coverage.js b/test/unit/externals/output-coverage.js
index 2d6a579b..a3d9ca2c 100644
--- a/test/unit/externals/output-coverage.js
+++ b/test/unit/externals/output-coverage.js
@@ -7,6 +7,14 @@
 "use strict";
 module.exports = require("externalmapped");
 
+/***/ }),
+
+/***/ 196:
+/***/ ((module) => {
+
+"use strict";
+module.exports = require("regexexternal");
+
 /***/ })
 
 /******/ 	});
@@ -49,8 +57,11 @@ var __webpack_exports__ = {};
 // This entry need to be wrapped in an IIFE because it need to be isolated against other modules in the chunk.
 (() => {
 const external = __nccwpck_require__(306);
+const regexpExternal = __nccwpck_require__(196);
 
 console.log(external);
+console.log(regexpExternal);
+
 
 })();
 
diff --git a/test/unit/externals/output.js b/test/unit/externals/output.js
index 2d6a579b..a3d9ca2c 100644
--- a/test/unit/externals/output.js
+++ b/test/unit/externals/output.js
@@ -7,6 +7,14 @@
 "use strict";
 module.exports = require("externalmapped");
 
+/***/ }),
+
+/***/ 196:
+/***/ ((module) => {
+
+"use strict";
+module.exports = require("regexexternal");
+
 /***/ })
 
 /******/ 	});
@@ -49,8 +57,11 @@ var __webpack_exports__ = {};
 // This entry need to be wrapped in an IIFE because it need to be isolated against other modules in the chunk.
 (() => {
 const external = __nccwpck_require__(306);
+const regexpExternal = __nccwpck_require__(196);
 
 console.log(external);
+console.log(regexpExternal);
+
 
 })();