THMX file format is associated with Microsoft Office 2007 version software application. This file format is used to change the appearance of the application.

The THMX file format contains information related to font style, color and graphic effect for a specific file or document. All the elements which the user can add to a specific file or document is already defined by the THMX file and hence when the user applies it to a specific document all the user changeable elements are automatically edited or changed by the theme file. THMX file format is used to define documents in MS Word, PowerPoint, Excel and Outlook.