Aidan Quinn (born March 8, 1959) is an American actor who made his film debut in Reckless (1984). He has starred in over 80 feature films, including Desperately Seeking Susan (1985), The Mission (1986), Stakeout (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), and Unknown (2011).
Quinn has received two Primetime Emmy Award nominations for his work in An Early Frost (1985) and Bury My Heart at Wounded Knee (2007). He played Captain Thomas "Tommy" Gregson in the CBS television series Elementary (2012–2019).
In Mary Shelley's Frankenstein (1994), Quinn plays Captain Robert Walton. This is a rare film appearance by Walton, who is one of the three first-person narrators of the source novel (the other two narrators being Victor Frankenstein and his creation), but who is left out of virtually every other performing arts adaptation.