Charles Peckham Day (born February 9, 1976) is an American actor, screenwriter, producer, director and musician. He is best known for playing Charlie Kelly on It's Always Sunny in Philadelphia for which he was nominated for the Critics' Choice Television Award for Best Actor in a Comedy Series in 2011. In film, he is known for his role as Dale in the films Horrible Bosses (2011) and its 2014 sequel, as well as for his roles in Monsters University (2013), Pacific Rim (2013), The Lego Movie (2014), Fist Fight (2017), Pacific Rim: Uprising (2018), and The Lego Movie 2: The Second Part (2019). From 2018 to 2019, Day was the executive producer on the Fox comedy The Cool Kids.
Day was born in The Bronx, in New York City, but spent most of his childhood in Middletown, Rhode Island. He is the younger child of two, with an older sister named Alice. His mother, Mary (née Peckham), was a piano teacher at The Pennfield School in Portsmouth, Rhode Island, and his father, Dr. Thomas Charles Day, is a retired professor of music history at Salve Regina University in Newport, Rhode Island. His family's original surname was "Del Giorno" and his father is of Irish and Italian descent., while his mother has English, Irish, and Welsh ancestry.