A subscriber to a channel on the American video-sharing platform YouTube is a user who has chosen to receive the channel's content by clicking on that channel's "Subscribe" button, and each user's subscription feed consists of videos published by channels to which the user is subscribed. The ability for users to subscribe was introduced in October 2005. YouTube began publishing a list of its most-subscribed channels in April 2006. An early archive of the list dates to May 17, 2006.

Since May 2006, when Smosh occupied the top position with just 2,986 subscribers, at least 11 other YouTube channels have held the top spot; these include the channel for the American fictional web series lonelygirl15, American comedian Brooke "Brookers" Brodack, American fictional character Fred Figglehorn, Swedish gamer Felix "PewDiePie" Kjellberg, American comedian Ryan Higa, American media personality Ray William Johnson, American public speaker Judson Laipply, English pensioner Peter Oakley, and the official channels for Indian music record label T-Series, as well as YouTube itself.

The most-subscribed YouTube channel is MrBeast, having 405 million subscribers as of June 15, 2025, and gaining subscribers by an average of about 320,000 per day.