Thomas Ellis Gibson (born July 3, 1962) is an American actor and director. He is known for having portrayed Daniel Nyland in the CBS series Chicago Hope, Greg Montgomery on the ABC series Dharma & Greg, and Aaron Hotchner on the CBS series Criminal Minds (2005–2016).
Gibson was born in Charleston, South Carolina, the youngest of four children of Charles M. "Mac" and Beth Gibson. His mother was a social worker, and his father was a lawyer and liberal Democrat who served in the South Carolina state Senate and House. He was raised Roman Catholic. Gibson's interest in the performing arts began at a young age. Gibson was fascinated with Louis Armstrong. He and his sister were on a swim team together and they frequented a pizza parlor after their swim meets. It was at this pizza parlor that Gibson would sing along with a Dixieland band, complete with his attempt at a Louis Armstrong voice.