YouTube is a video-sharing website headquartered in San Bruno, California. The service was created by three former PayPal employees in February 2005. In November 2006, it was bought by Google for US$1.65 billion. YouTube now operates as one of Google's subsidiaries. The site allows users to upload, view, and share videos, and it makes use of Adobe Flash Video and HTML5 technology to display a wide variety of user-generated and corporate media video. Available content includes video clips, TV clips, music videos, and other content such as video blogging, short original videos, and educational videos.

Most of the content on YouTube has been uploaded by individuals, but media corporations including CBS, the BBC, Vevo, Hulu, and other organizations offer some of their material via YouTube, as part of the YouTube partnership program.Unregistered users can watch videos, and registered users can upload videos to their channels. Videos considered to contain potentially offensive content are available only to registered users affirming themselves to be at least 18 years old.

YouTube was founded by Chad Hurley, Steve Chen, and Jawed Karim, who were all early employees of PayPal. Hurley had studied design at the Indiana University of Pennsylvania, and Chen and Karim studied computer science together at the University of Illinois at Urbana-Champaign.

According to a story that has often been repeated in the media, Hurley and Chen developed the idea for YouTube during the early months of 2005, after they had experienced difficulty sharing videos that had been shot at a dinner party at Chen's apartment in San Francisco. Karim did not attend the party and denied that it had occurred, but Chen commented that the idea that YouTube was founded after a dinner party "was probably very strengthened by marketing ideas, around creating a story that was very digestible".