Mary Elizabeth Ellis is an American actress and writer. She is known for her role as The Waitress on the FX sitcom It’s Always Sunny in Philadelphia with Rob McElhenney, Kaitlin Olson, Glenn Howerton, and Danny DeVito. Ellis also starred in the NBC sitcom Perfect Couples and the Fox sitcom The Grinder. She also appeared as Nick’s ex-girlfriend Caroline in the sitcom New Girl. From 2017 to 2019, she starred as Lisa Palmer on the Netflix horror-comedy Santa Clarita Diet.
Ellis married her It’s Always Sunny in Philadelphia co-star Charlie Day on March 4, 2006. Their first child, a boy named Russell Wallace Day, was born on December 15, 2011.