Arabella Helen Weir (born 6 December 1957) is an American-born British comedian, actress, and writer. She is best known for her roles in the comedy series The Fast Show, Posh Nosh, and Two Doors Down. Weir has penned several books, most notably Does My Bum Look Big in This?

In addition to her acting and writing career, Weir has contributed to The Independent and The Guardian, including the latter's Weekend magazine. In 2006, she voiced an alternative third incarnation of the Doctor for Big Finish's Unbound audio range.