Smosh is an American YouTube sketch comedy-improv collective, independent production company, and former social networking site founded by Anthony Padilla and Ian Hecox. In 2002, Padilla created a website named "smosh.com" for making Flash animations, and he was later joined by Hecox. They began posting videos on Smosh's YouTube channel in 2005 and quickly became one of the most popular channels on the site. As of 2024, the channel has over 10 billion views and over 26 million subscribers.

Since 2012, the Smosh brand has expanded to consist of multiple channels, including a Spanish-language channel (ElSmosh), a channel focused on gaming content (Smosh Games), and a variety channel (Smosh Pit), while also expanded to a larger cast featured throughout their content. The Smosh channel has experienced three different spans as the most-subscribed YouTube channel. The first period spanned from May to June 2006, the second from April 2007 to September 2008, and the third span from January to August 2013.

In 2017, Padilla left the channel to pursue independent ventures and focus on his own separate channel. On November 6, 2018, Smosh's then-parent company Defy Media abruptly closed without warning. Six days later, the Smosh cast released a video announcing that production of Smosh, Smosh Pit, and Smosh Games content was still ongoing, and that existing videos would be finished and other content would be released independently on those channels. Smosh subsequently joined Mythical Entertainment after the company was purchased by Rhett & Link on February 22, 2019. After four years of ownership under Mythical, it was announced in June 2023 that Padilla had returned to the channel, and that he, along with Hecox, had bought the company back from Mythical, re-establishing Smosh as an independent entity.