Aidan Quinn (born March 8, 1959) is an American actor. He made his film debut in Reckless (1984) and has starred in over 80 feature films, including Desperately Seeking Susan (1985), The Mission (1986), Stakeout (1987), All My Sons (1987), Avalon (1990), Benny & Joon (1993), Legends of the Fall (1994), Mary Shelley's Frankenstein (1994), Michael Collins (1996), Practical Magic (1998), Song for a Raggy Boy (2003), Wild Child (2008) and Unknown (2011). He also played Captain Thomas "Tommy" Gregson on the CBS television series Elementary (2012–19).

Quinn has received two Primetime Emmy Award nominations for his performances in the television films An Early Frost (1985) and Bury My Heart at Wounded Knee (2007). Highly active in Irish cinema and the United States, Quinn is a four-time Irish Film and Television (IFTA) Award nominee, winning Best Supporting Actor in a Film for the Conor McPherson film The Eclipse (2009).