A prolific character actor known for playing "slimy villains, tough cops, and military officers,"[1] he worked with notable directors like Bob Rafelson, Francis Ford Coppola, Andrei Konchalovsky, Arthur Penn, Philip Kaufman, and The Wachowskis, and often appeared in films starring his friend Jack Nicholson.

[1][2] Ryan was born in New York City, the son of Irish immigrant parents, and graduated from Rice High School in Harlem.

[3] Among his stage roles, Ryan played King Henry in The Lion in Winter and Mr. DePinna in You Can't Take It with You at the 1966 Williamstown Theatre Festival.

[1] He appeared opposite Nicholson in Five Easy Pieces (1970), The King of Marvin Gardens (1973), The Missouri Breaks (1976), The Postman Always Rings Twice (1981), and Hoffa (1992).

He also appeared in such films as Dillinger (1973), Futureworld (1976), Breathless (1983), The Right Stuff (also 1983), The Cotton Club (1984), Three O'Clock High (1987), and Best of the Best (1989).