A webmaster (portmanteau of web and postmaster), also called a web architect, web developer, site author, website administrator, or (informally) webmeister, sometimes heard in tongue-in-cheek feminine form web mistress, is a person responsible for maintaining a website(s). The duties of the webmaster may include ensuring that the web servers, hardware and software are operating accurately, designing the website, generating and revising web pages, replying to user comments, and examining traffic through the site. Webmasters "must also be well-versed in Web transaction software, payment-processing software, and security software."

Webmasters may be generalists with HTML expertise who manage most or all aspects of Web operations. Depending on the nature of the websites they manage, webmasters typically know scripting languages such as Javascript, PHP and Perl. They may also be required to know how to configure web servers such as Apache or IIS and serve as the server administrator.

An alternative definition of webmaster is a businessperson who uses online media to sell products and/or services. This broader definition of webmaster covers not just the technical aspects of overseeing Web site construction and maintenance but also management of content, advertising, marketing and order fulfillment for the Web site.

Core responsibilities of the webmaster may include the regulation and management of access rights of different users of a website, the appearance and setting up website navigation. Content placement can be part of a webmaster's responsibilities, while content creation may not be.