In the spring of 1963, Steve McQueen was on the brink of superstardom, already popular from his big-screen breakout as one of The Magnificent Seven and just a couple months away from entering the Badass Hall of Fame with the release of The Great Escape.
Intrigued by his dramatic backstory and his off-screen exploits — McQueen was a reformed delinquent who got his thrills racing cars and motorcycles — LIFE sent the great photographer John Dominis to California to hang out with the 33-year-old actor and, in effect, see what he could get.
Three weeks and more than 40 rolls of film later, Dominis had captured some astonishingly intimate and now-iconic images — photos impossible to imagine in today’s utterly restricted-access celebrity universe. Only a handful of those photos were ever published. Here, LIFE.com presents a series of previously unpublished gems from what Dominis would look back on as one of his favorite assignments, along with insights about the time he spent with the man who would soon don the mantle, “the King of Cool.”
Full slide show here.