The Queen of Pop hit the milestone this Friday, and a day later posted a series of snaps on her Instagram showing her with Jamaican footballer Akeem Morris, 28, who has been holidaying with her in Italy on a days-long birthday celebration.
She captioned the images, which included snaps of her lighting up a long cigarette for him and him blowing smoke around them: "Back in Italy... Happy Birthday to ME."
Madonna also posed in a corset on a bed in an echo of one of her raunchiest stage show set-ups.
The 'Material Girl' singer has been seen walking arm-in-arm in Italy's Portofino in the last week with Madonna.
She toured the 2,200-year-old Teatro Grande amphitheatre, as part of the trip, according to the Daily Mail.
The Mail reported Madonna has been on holiday in Italy for the past week, after previously hosting a string of birthdays in the country - including in Noto, Sicily and Borgo Egnazia.
The lingerie-style outfit she sported in her 66th birthday snaps included a
suspender belt and fishnets made by Italian designers Dolce and Gabbana.
It has emerged in the past week Madonna first met her rumoured new love Akeem in 2022 when they appeared in a shoot together in the Paper magazine.
They weren't seen together again until July, when the musician posted snaps of him on her Instagram.
Madonna's images showed her cuddling up to the footballer on 4 July as they celebrated the US holiday together in New York.
She has also posted a picture of herself in bed with Akeem that was captioned: "Hot Fun In The Summer Time."
Akeem lives in New York after being born in Jamaica, the Mail has reported, which also said he has a degree in political science and government after studying at Stony Brook University between 2014 and 2017.
During his time at university, Akeem played soccer and also was a forward for Oyster Bay United football club, according to ESPN.