John Arthur Rubinstein (born December 8, 1946) is an American film, Broadway, and television actor, a composer of film and theatre music, and a director in theatre and television.

Rubinstein was born in Los Angeles, the son of Aniela (née Młynarska), a dancer and writer, and the concert pianist Arthur Rubinstein. Rubinstein's maternal grandfather was Polish conductor Emil Młynarski.

He made his Broadway acting debut in 1972 and received a Theater World Award for creating the title role in the musical Pippin, directed by Bob Fosse. In 1980 he won the Tony, Drama Desk, Los Angeles Drama Critics Circle, and Drama-Logue Awards for his portrayal of James Leeds in Mark Medoff's Children of a Lesser God, directed by Gordon Davidson. Other Broadway appearances were in Neil Simon's Fools, directed by Mike Nichols, and Herman Wouk's The Caine Mutiny Court-Martial, which earned him a Drama Desk nomination; he replaced William Hurt as Eddie in David Rabe's Hurlyburly, replaced David Dukes in David Henry Hwang's M. Butterfly, and starred in Getting Away with Murder, by Stephen Sondheim and George Furth, directed by Jack O'Brien. In 1987 he made his off-Broadway debut at the Roundabout Theater as Guildenstern in Tom Stoppard's Rosencrantz & Guildenstern Are Dead, with Stephen Lang and John Wood, and subsequently performed in Urban Blight and Cabaret Verboten. In 2005 he received the Lucille Lortel Award for Best Lead Actor in a Play, as well as nominations for both the Outer Critics’ and Drama League Awards, for his portrayal of George Simon in Elmer Rice's Counselor-at-Law. In addition, he has made numerous appearances in regional theatre productions.

Rubinstein's feature films include 21 Grams, Red Dragon, Mercy, Another Stakeout, Someone to Watch Over Me, Daniel, The Boys from Brazil, Rome and Jewel, Jekyll, Kid Cop, Getting Straight, Zachariah, The Trouble with Girls, and The Car. Since 1965 he has acted in over 150 television films and series episodes. He received an Emmy Award nomination for his portrayal of Jeff Maitland in the series Family, a role he played for five years, starred for two years with Jack Warden in the series Crazy Like a Fox, and was featured in the miniseries Perfect Murder, Perfect Town. He has subsequently played recurring parts on Angel, The Guardian, The Practice, Star Trek: Enterprise, and BarberShop. In the series finale of Friends, he played the doctor who delivered Monica and Chandler's babies.

Rubinstein has composed, orchestrated, and conducted the musical scores for five feature films, including Jeremiah Johnson and The Candidate, as well as for over 150 television films and episodes. He spent six years as host for the radio program Carnegie Hall Tonight, broadcast on 180 stations in the United States and Canada, and two years as the keyboard player for the jazz-rock group Funzone. He has also recorded over sixty-five books on audio, including eighteen of the best-selling Alex Delaware novels by Jonathan Kellerman.

In 1987, Rubinstein made his directorial debut at the Williamstown Theater Festival, staging Aphra Behn's The Rover, with Christopher Reeve. He has continued to direct regional theater productions, as well as in television.

He is currently playing The Wonderful Wizard of Oz in the Los Angeles production of Wicked.

The multi-faceted actor/singer/composer/director John Rubinstein was born in Los Angeles in 1946, the same year his father, the internationally renown Polish concert pianist Artur Rubinstein, became an American citizen. John naturally gravitated toward a career in music. Slim and sensitive-looking, he attended UCLA before making his 1972 Broadway debut as the baby-faced, curly-haired title role in the popular musical "Pippin" for which he received a Theater World Award. As a composer he put the film scores of Robert Redford (I)'s Candidate, The (1972) and Jeremiah Johnson (1972) together, and got off to an OK start on-camera in the movies Getting Straight (1970) and Zachariah (1971) (title role). Though he never achieved out-and-out stardom, John biggest claim to fame would occur on Broadway later in the 1970s when he starred in "Children of a Lesser God,", which won him the Tony, Drama Desk and L.A. Drama Critics Circle Awards. A bigger movie marquee name, William Hurt (I), would reenact his role when the play transferred to film. Other Big Apple appearances would include "Fools", "The Caine Mutiny Court-Martial" (Drama Desk nomination), "Hurlyburly", and "M. Butterfly", and he originated the male counterpart in the popular two-person play "Love Letters" in 1989. As he matured, John grew into stronger corporate roles, some deceptively cunning and decisively slick, notably on TV, wherein he essayed the role of MGM mogul Irving Thalberg in the mini-movie Silent Lovers, The (1980) (TV). He won an Emmy Award nomination for his recurring ex-husband role on the popular drama series _"Family" (1976/III), for which is was also responsible for the music. John went on to compose, orchestrate and conduct the scores to over 50 TV shows and mini-movies. A prolific stage and TV director notwithstanding, he co-helmed the L.A. revival of Elmer Rice's Counsellor-At-Law, in which he also played the title role, as well as a number of established musicals including "Into the Woods" and "A Little Night Music." He has directed TV episodes of "Nash Bridges" (1996) and "High Tide" (1994), among others and in recent years, has appeared in fine stage form in "Ragtime" and "Enigmatic Variations.". Married twice, John has four children.