Born Robert McMillan in a Glasgow neighborhood, Coltrane was the middle child (and only son) of teacher mother and a physician father, who worked at one time as a police surgeon. During his adolescence, he used comedy to deflect the taunts of his schoolmates and contemplated following in his older sister's wake as an artist. While studying painting, Coltrane concluded that his work did not meet his own high standards and gradually drifted to film. In 1973, he made a 50-minute documentary titled "Your Mental Health" that earned awards and critical notice.

With renewed purpose, Coltrane (who adopted his stage surname in tribute to jazz musician John Coltrane) spent the 1970s honing his craft on stage, including appearances in John Byrne's "The Slab Boys". At the same time, he also began to engage in improvisatory work and eventually developed a nightclub act. By the end of the decade, he finally made his acting debut in "Deathwatch" (1979), directed by Bernard Tavernier.

For much of the 1980s, Coltrane alternated between TV and film. The small screen afforded him opportunities to demonstrate his comedic abilities on such efforts as "Metal Mickey", "The Comic Strip Presents" and "Tutti Frutti". On the silver screen, Coltrane has his first major role as a police detective tracking a killer in "Subway Riders" (1981), helmed by Amos Poe. He went on to work with Chevy Chase in "European Vacation" and Al Pacino in the forgettable "Revolution" (both 1985). Coltrane won notice for his turn as Bob Hoskins' mechanic pal in the superior "Mona Lisa" and as the corrupt cardinal in the Derek Jarman-directed "Caravaggio" (both 1986). Kenneth Branagh tapped the actor to play Falstaff in the 1989 remake "Henry V.”

As the 90s dawned, Coltrane returned to comedy with a pair of humorous performances. In "Nuns on the Run" (1990), he was teamed with Eric Idle as gangsters evading capture by disguising themselves as religious women, while in "The Pope Must Die" (1991), he portrayed the pontiff who was targeted for murder. But 1993 marked a turning point for the actor when he was tapped to play Eddie 'Fitz' Fitzgerald, a fictional character who embraced life's vices and virtues with glee and excess, yet who was also good at his job, in "Cracker". Amazing at it may seem now, but Coltrane was not the first choice for the role and only was cast after the producers' pick – Robert Lindsay – had to pass on the show. Coltrane and Fitz were a perfect match and the actor was rewarded for his efforts with three consecutive BAFTA TV awards as Best Actor. Even as he amassed prizes for the series, the actor continued to appear in films, playing everything from the husband of a woman who raises a gorilla in "Buddy" (1997) to an American newspaper editor in "Message in a Bottle" (1999). Just prior to delighting audiences as Hagrid, Coltrane was once again cast as a Scottish detective, this time a man of the 19th Century on the track of London's most notorious serial killer -- Jack the Ripper -- in the Hughes Brothers' film "From Hell" (2001).

In 2002, Coltrane was cast as Rubeus Hagrid in "Harry Potter and the Sorceror's Stone" (2001) , a role that he reprised in the sequels "Harry Potter and the Chamber of Secrets (2002) and "Harry Potter and the Pirsoner of Azkaban" (2004). He also provided the threatening voice of the monstrous Mr. Hyde, a CGI creation in "Van Helsing" (2004). Once again, Coltrane revived his beloved role as Hagrid for the fourth in the series, “Harry Potter and the Goblet of Fire” (2005), the first installment to be helmed by a British director (Mike Newell).