Marnie McPhail Diamond is a well-known Canadian actress and musician of American origin. She rose to fame for her roles as Maria Wong in the series Braceface, Annie Edison in The Edison Twins, and Peaches in JoJo's Circus.

McPhail was born and raised in Columbus, Ohio, USA. She later moved to Toronto, Ontario, where she studied at the Etobicoke School of the Arts. At the age of 14, she got her first major role — Annie Edison in the children's television series The Edison Twins (1982).

On the set of the film The Scared Silent (2002), McPhail met her husband Reid Diamond, and since 2004 they have been happily married. Both McPhail and her husband are members of the rock band Chuck Valiant: McPhail is the vocalist, and Diamond plays guitar.