Note: This article is pretty old. Check the comments for people's experiences with newer versions of Chrome.

If you are using Chrome Beta:

  1. Quit Chrome

  2. Edit ~/Library/Application\ Support/Google/Chrome/Default/Preferences

  3. Add an entry that says:

    "spellcheck": {

    "dictionary": ""

    }

  4. Restart Chrome

When you add the entry at the end of the file, make sure to add a "," at the end of the previous entry. The result should look something like this:

...
   "webkit": {
      "webprefs": {
         "inspector_settings": "lastActivePanel:string:scripts\n"
      }
   },
   "spellcheck": {
      "dictionary": ""
   }
}

If you are using Chromium, the file is ~/Library/Application\ Support/Chromium/Default/Preferences.