Sir William Connolly, (born 24 November 1942) is a Scottish comedian, musician, presenter and actor from Glasgow. He is sometimes known, especially in his homeland, by the nickname "The Big Yin" ("The Big One"). His first trade, in the early 1960s, was as a welder (specifically a boilermaker) in the Glasgow shipyards, but he gave it up towards the end of the decade to pursue a career as a folk singer, firstly in the Humblebums alongside friend Gerry Rafferty and Tam Harvey until 1971, and subsequently as a solo artist. In the early 1970s, Connolly made the transition from folk-singer with a comedic persona to fully fledged comedian, for which he has received numerous awards.

Connolly is also an actor and has appeared in such films as Water (1985), Indecent Proposal (1993), Pocahontas (1995), Muppet Treasure Island (1996), Mrs. Brown (1997), The Boondock Saints (1999), The Man Who Sued God (2001), The Last Samurai (2003), Timeline (2003), Lemony Snicket's A Series of Unfortunate Events (2004), Garfield: A Tail of Two Kitties (2006), Open Season (2006), The X-Files: I Want to Believe (2008), Open Season 2 (2008), Brave (2012), Quartet (2012), and The Hobbit: The Battle of the Five Armies (2014). Connolly reprised his role as Noah "Il Duce" MacManus in The Boondock Saints II: All Saints Day (2009).