Britney Spears has described the termination of a legal arrangement that controlled many aspects of her life for 13 years as "the best day ever".

"I think I'm gonna cry," she told her 35 million Instagram followers.

A judge in Los Angeles on Friday ended the conservatorship set up by the 39-year-old singer's father in 2008 with immediate effect.

Fans had gathered outside the LA court to support Spears, who had described the guardianship as abusive.

Her father Jamie 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.

On Friday, Los Angeles County Superior Court Judge Brenda Penny ruled in favour of the singer's request to end it, which was not opposed by any of the parties involved.