A judge in Los Angeles on Friday ended the guardianship set up by the 39-year-old's father in 2008 "effective today".
Fans had gathered outside the LA court to support the singer, who had described the set up as abusive.
Her father earlier said it was "necessary", but agreed it was time for her "to re-take control of her life".
"Her life was in shambles and she was in physical, emotional, mental and financial distress," lawyers representing Jamie Spears said in earlier court filings.
The conservatorship had power over her finances and career decisions plus major personal matters such as her visits with her teenage sons and whether she can get remarried.