A professional website is an internet site where the content can be deemed reasonably trustworthy because it is provided by professionals with a working knowledge of the topic. The reliability of this source type falls between that of an official and a user-generated website, as professional sources may have a reputation to uphold but also may lack direct access to high-level data sources.

Examples of professional websites include the internet pages of governments, institutions, realtors, professional organizations, publishers, and news organizations.

The relevant content is supplied by people with professional knowledge of its subject. A professional organization's website is not automatically the object owner's official website; professional expertise and direct ownership-based access establish different relationships to the information.