A Microsite, also known as a minisite or weblet, is an Internet web design term referring to an individual web page or cluster of pages which are meant to function as an auxiliary supplement to a primary website. The microsite's main landing page most likely has its own domain name or subdomain.

They are typically used to add a specialized group of information either editorial or commercial. Such sites may be linked in to a main site or not or taken completely off a site's server when the site is used for a temporary purpose. The main distinction of a microsite versus its parent site is its purpose and specific cohesiveness as compared to the microsite's broader overall parent website.

Microsites may be used for purely commercial purposes to create in-depth information about a particular product, service or as editorial support towards a specific product, such as describing a new technology. A car manufacturer, for example, may present a new hybrid vehicle and support the sales presentation with a microsite specific to explaining hybrid technology.