Received a Bachelor of Fine Arts degree from DePaul University's Goodman School of Drama (Chicago) 
Originated the role of Marty in the 2002 musical "Marty" (book by Rupert Holmes, music by Charles Strouse, lyrics by Lee Adams), based on the 1955 movie Marty (1955).
In April 2004, he left the filming of Manderlay (2005) to be replaced by Slovenian actor Zeljko Ivanek. According to a report in Entertainment Weekly, he did so to protest against the killing of a donkey during production.
Attended DePaul University in Chicago.
John is a wonderful singer who came out of a musical theater background. He did all of his own singing in Chicago (2002).
In 2003, he starred in three out of the five movies nominated for Best Picture. They are Chicago (2002), Gangs of New York (2002), and The Hours (2002). All of these films were produced by Miramax Films.
Made a home video of himself singing in a bow tie and suit for director Rob Marshall who gave him his role in Chicago (2002).
John's father's ancestry was three quarters Irish, one eighth German, one sixteenth French-Canadian, and one sixteenth Scottish. John's maternal grandparents, Clemens Petronis and Veronica Strelciunas, were Lithuanian. He is the fifth of six children.
Director Antoine Fuqua wanted to cast him in his since aborted crime epic "Tru Blu" with Denzel Washington and Benicio Del Toro.
For not only his broad, almost 6' 2" frame, curly hair, and everyman's mug, but also his straight-forward but thoughtful acting style, Reilly has frequently been dubbed "his generation's Gene Hackman".
Was nominated for Broadway's 2000 Tony Award as Best Actor (Play) for a revival of Sam Shepard's "True West."
Graduated from Brother Rice High School on the South Side of Chicago.
In addition to having worked with Leonardo DiCaprio in The Aviator (2004), he has also worked with two other actors who played Howard Hughes: Jason Robards (from Melvin and Howard (1980)) in Magnolia (1999), and Tommy Lee Jones (from The Amazing Howard Hughes (1977)) in A Prairie Home Companion (2006).
Was member of the dramatic jury at the Sundance Film Festival in 2005.
Is a Chicago White Sox fan.
Lost a few pounds to play the rock star title character in Walk Hard: The Dewey Cox Story (2007).
In the tradition of Alan Young's Filby from The Time Machine (1960), Reilly plays a teenager aged 14 in his forties - aged 41, for Walk Hard: The Dewey Cox Story (2007).
He met his wife in Thailand while he was filming Casualties of War (1989), who, at the time, was Sean Penn's assistant.
His first plane ride was to Thailand to film Casualties of War (1989).
Will play the iconic role of Stanley Kowalski in the Roundabout Theatre Company's revival of Tennessee Williams' "A Streetcar Named Desire". [March 2005]
Has frequently played a naive husband, oblivious to his wife's resentment of him, in Chicago (2002), The Hours (2002) and We Need to Talk About Kevin (2011).
As of 2015, has appeared in five films that were nominated for the Best Picture Oscar: The Thin Red Line (1998), Chicago (2002), The Hours (2002), Gangs of New York (2002) and The Aviator (2004). Of those, Chicago (2002) is a winner in the category.
Appeared in four films along Sean Penn: Casualties of War (1989), We're No Angels (1989), State of Grace (1990) and The Thin Red Line (1998).
Friends with Will Ferrell.
Nominated for the 2019 Golden Globe Award in the Best Performance by an Actor in a Motion Picture - Musical or Comedy category for his role as Oliver Hardy in Stan & Ollie (2018), but lost to Christian Bale for Vice (2018).