Andrew O'Neill (born 14 September 1979) is a British comedian, musician, presenter, and writer who lives in London.

Born in Portsmouth in 1979, O'Neill grew up in the London suburban town of Wallington. They have two brothers, Steve and David. They did their first comedy performance at the age of ten, and started their stand-up career on 16 January 2002 at the Laughing Horse, Camden. They have since gone on to perform in comedy clubs, theatres and music festivals throughout the UK, Australia, US and Europe.

O'Neill has described themself as "a vegan, heterosexual transvestite, who happens to be a metalhead and amateur occultist". O'Neill is non-binary, uses they/them pronouns.

Andrew is a regular on the comedy stage at Download Festival, played to 5,500 people at Sonisphere Festival, opened for Amanda Palmer from The Dresden Dolls, and has performed at comedy festivals in Adelaide, Melbourne and Wellington. They have a column in Terrorizer magazine.

O'Neill is the guitarist for steampunk band The Men That Will Not Be Blamed For Nothing.

In 2017 they published their first book, A History of Heavy Metal. It was described by Alan Moore as "a comprehensive landmark analysis of an enormous area of music that has been too long without such a thing, and has the massive advantage of the funny being turned up to twelve. A loud and thoroughly engrossing love-story."

In 2023 they appeared as Mutt's Spouse in Series 2 of Good Omens.