NetSurf is an open source web browser which has its own layout engine. It is designed to be lightweight and portable, supporting both mainstream systems (e.g. Mac OS X and Unix-like) and older or uncommon platforms (e.g. AmigaOS, Haiku and RISC OS). NetSurf has many typical web browser features, including tabbed browsing, bookmarks and page thumbnailing.

The NetSurf project was started in April 2002 in response to a discussion of the deficiencies of the RISC OS platform's existing web browsers. Shortly after the project's inception, development versions for RISC OS users were made available for download by the project's automated build system. NetSurf was voted "Best non-commercial software" four times in Drobe Launchpad's annual RISC OS awards between 2004 and 2008.

The browser was ranked in 2011 as number 8 in an article highlighting 10 browsers for Linux published in TechRepublic and ZDNet. It was referred to in 2010 as a superior CLI browser to w3m.

NetSurf's multi-platform core is written in ANSI C, and implements most of the HTML 4 and CSS 2.1 specifications using its own bespoke layout engine. As of version 2.0, NetSurf uses Hubbub, an HTML parser that follows the work-in-progress HTML5 specification. As well as rendering GIF, JPEG, PNG and BMP images, the browser also supports formats native to RISC OS, including Sprite, Draw and ArtWorks files. It was suggested by developer John-Mark Bell in 2007 that support for JavaScript could be added. As of 2011^[update], NetSurf has no support for it.