The celebrations began on Sunday night when the singer hosted a sumptuous dinner party in the Italian resort of Portofino, where she is staying with her boyfriend Jesus Luz, her adopted children David Banda and Mercy James, and her daughter Lourdes.
Madonna, wearing personalised basketball kit, leaped into the sea while on a break in Portofino, Italy.
For the party she hired an entire floor of the exclusive Splendido Hotel where suites cost as much as £4,500 a night.
She was joined by around 30 guests, including Italian fashion designers Domenico Dolce and Stefano Gabbana. They presented her with a huge cake with sparklers on top and a specially-designed lace dress.
Throughout the meal, Madonna was seen kissing Jesus, whom she met in December last year shortly after splitting from Guy Ritchie.
The star took a dip with her toyboy and they float towards each other in the water. He seems to have taken on the role of father figure to David, three, and Mercy, four, judging by the way he was carrying and playing with them during the day.
Madonna was taken by private boat along with her two adopted children and Jesus to the home of the two designers, where she continued her celebrations.
Dressed in a personalised basketball kit, she was seen taking an acrobatic leap into the sea as the rest of the party looked on.
The singer defended her lifestyle last year when she said: 'Once you reach a certain age you're not allowed to be adventurous, you're not allowed to be sexual. I mean, is there a rule? Are you supposed to just die? I've never been a conformist.'
Madonna kicked off her birthday celebrations early on Saturday when thousands of Polish fans wished her happy birthday at her Warsaw concert.
Fans held up signs saying happy birthday and sang May You Live A Hundred Years, a traditional Polish birthday song. A grateful Madonna said: 'I feel your love. I love what I do, but you regenerate me.'