The actress and singer Jayne Mansfield (born Vera Jayne Palmer on April 19, 1933) was one of those quintessentially American pop-culture creations who helped define the country's mood — playful, naive, expansive — in the middle part of the 20th century. That she was also, in large part, a self-created icon who reveled in publicity stunts only added, and still adds today, to her appeal: it's difficult, after all, to dislike someone who so giddily pursues fame, and who so exuberantly embraces it once it's attained.
Here, on Jayne Mansfield's 81st birthday, LIFE.com remembers the archetypal blonde bombshell with a series of photos — none of which ran in LIFE magazine — made by Peter Stackpole in the spring of 1956. Mansfield was in her early 20s at the time and, while she was not yet a full-fledged movie star, she was clearly someone to watch; she had already made a name for herself on Broadway and was, it seemed, destined for bigger things on the silver screen. As LIFE wrote in an April 1956 issue:
Though the thought has never crossed her pretty blond head, Jayne Mansfield is one of the most interesting sociological studies to be found anywhere in the U.S. this spring. Miss Mansfield has burst dazzlingly upon the theatrical world as a star of a Broadway comedy called Will Success Spoil Rock Hunter? and currently seems to be getting her name and photograph into more Broadway columns and movie magazines than any other actress alive. . . . Miss Mansfield is still just herself, friendly and frank, perhaps even somewhat naive in her own calculating way. This is a rare situation, for ordinarily a movie queen is presented to the public only after some studio has gone to immense expense changing her over completely, to the point where her own mother would not recognize her.
Miss Mansfield does not even obey cliché No. 1 of the movie queen, which is to act bored with success. No teen-ager ever exhibited so much tenacity at seeking autographs as she does at signing them; she will stand in wind, rain or snow until her last admirer is satisfied.
She has the same come-hither-you-brute sort of voice and look as Marilyn Monroe. But the comparison, which a more seasoned actress would at least pretend to love, does not seem to please Miss Mansfield at all. "Marilyn is very attractive and all that," she has said, "but she and I are entirely different. I can dye my hair and play a serious part." For that matter Miss Mansfield would not even have to dye her hair. She could just let it grow back to its natural color, which she admits, again in gross violation of the movie queen's code, is brown.
Despite her best efforts, however — and in spite of the fact that she was, after all, a talented actress and (classically trained) musician — Mansfield found it hard to get solid film roles, and her screen career was spotty after the mid-1950s. She did find great success (and riches) as a nightclub entertainer in her late 20s and early 30s, and — who knows? — might have parlayed that into a movie-career resurgence if her life had not been cut short. Riding home from a Mississippi nightclub in June 1967 with her lover at the time, Sam Brody, her driver Ronnie Harrison, and three children — Milkos Jr., Mariska [Hargitay, the actress], and Zoltan — Mansfield was killed when the car slammed into the back of a tractor-trailer. Brody and Harrison also died in the wreck; the kids, asleep in the backseat, made it out alive, with minor injuries.
(Contrary to popular, ghoulish myth, Mansfield was not decapitated in the wreck; she died from massive head trauma, and the story of her decapitation likely arose from gruesome photos of the crash scene that made their way into public in subsequent years.)
Jayne Mansfield was 34 when she died.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter at @LizabethRonk.