The photo was taken when the singer was in her twenties and still unknown
A nude photograph of pop star Madonna, taken in 1979, has sold for $37,500 (£26,000), at an auction in New York.
The explicit black and white picture was taken when Madonna was a dancer struggling to make ends meet.
An unnamed buyer bought the picture, which had been expected to fetch $15,000 (£10,365), said Christie's.
Meanwhile the singer topped Billboard's annual list of money-makers, following the unprecedented success of her Sticky & Sweet world tour.
The singer earned $242.2m (£167.7m), despite her album Hard Candy being only the 50th best-selling album of the year in the US.
MUSIC'S TOP EARNERS
1. Madonna - $242.2m
2. Bon Jovi - $157.2m
3. Bruce Springsteen - $156.3m
4. The Police - $110m
5. Celine Dion - $99.2m
Bon Jovi were second on the list with $157.2m (£108.8).
Each of the top five money-makers on the list toured in 2008, a year when recorded music sales fell once again.
The photo of Madonna was among 150 images from the collection of Leon and Michaela Constantiner, which included portraits of Linda Evangelista, Joan Crawford and Lana Turner.
The aspiring singer had replied to a newspaper advert by celebrated American photographer Lee Friedlander, who shot her for a series of nudes he was working on.
Madonna reportedly earned just $25 (£17) for the session. The photographer described her as "very confident, a street-wise girl".
Matthieu Humery, head of Christie's photography department, said the picture was "probably the most explicit" shot Friedlander took of the future pop icon.
The full-frontal image, and five others taken at the same session, were sold to Playboy in the 1980s.
A second picture of the singer, by Helmut Newton, sold at the same auction for $18,750 (£12,888), also beating an earlier estimate.
The image of Madonna in a short red dress while a man kneels beside her, contemplating her stockings, appeared in Playboy in the 1980s.
A Herb Ritts photo of Madonna's True Blue album cover, which sold for more than $15,000 in 2006, was previously the most expensive photograph of the singer to sell at auction, according to Christie's.