She had been in a head-to-head race with US President Barack Obama, who counted only 9.54 million fans, Us Magazine reported.
Michael Jackson, whose death just over a year ago sent his fans into mourning, counts the most fans on Facebook with some 14 million.
Lady Gaga thanked her fans in a short video message Friday for helping her reach the record.
It was the second triumph for the 24-year-old this week. Lady Gaga made fourth place on the Forbes magazine yearly Celebrity 100 list behind talk show queen Oprah Winfrey, singer Beyonce Knowles and Avatar director James Cameron.
The ranking considered her 62-million- dollar income along with television, magazine and internet appearances.