Michael Jackson’s “secret girlfriend” has been revealed as his children’s ousted nanny, Grace Rwaramba.

The romance between the late “Thriller” star and Ugandan-born Grace Rwaramba was reportedly an open secret among the singer’s staff and his three children, Prince Michael, 12, Paris Katherine, 11 and six-year-old Prince Michael II, who reportedly referred to Grace as “Mom.”

Last week, MJ’s former head of security, Matt Fiddes, admitted his ex-employer had a secret lover, but refused to name her, saying only that the mystery woman was not famous.

Rwaramba joined Jackson’s staff as a secretary in 1991. She was later promoted to the position of nanny for the singer’s children.

“Grace loved Michael and he loved her. The kids called her ‘Mom,’” says Ian Barkley, who was Michael’s personal photographer for three years.

A second bodyguard told Britain’s Sunday Mirror Newspaper: “Matt was referring to Grace. They were more like a married couple than employer and employee.”

“Grace was the closest person to Michael and the kids. She will be broken-hearted. The children were always their joint priority and like any couple they’d row if they disagreed about how they were being brought up,” says the security guard — who asked not to be identified.

“But the difference between Grace and other women in Michael’s life was that she had absolutely no interest in fame. It was something she actively avoided and Michael was determined to keep her and their relationship out of the public gaze.”

“The romance was well-known among staff but it was made very clear to them that this was not something that should become part of the public domain.”