Scotland Yard said that, of the 200 individuals, the vast majority were victims of the late BBC presenter and were abused as children, but that the figure also included victims of alleged abuse by other individuals. It gave no names.
The Met had previously said that since Savile was dead it would conduct only a review into the allegations, in order that alleged victims could be officially acknowledged.
The force said the review had been broadened because it had established there were lines of inquiry involving living people that require formal investigation. Those people were not named, and the force did not elaborate further.
Commander Peter Spindler said a staggering number of victims had come forward, with more than 400 lines of inquiry being pursued.
"We are dealing with alleged abuse on an unprecedented scale," he said.
The NSPCC children's charity said Savile, who died on October 29, 2011, at the age of 84, may have been one of the most prolific sex offenders it had come across.
Former BBC director-general Greg Dyke has criticised the corporation's response to the Savile scandal.
He said the BBC should have moved very quickly to explain why a Newsnight report about allegations of sexual abuse by the late DJ was dropped.
Giving a lecture at Kingston University's Business School, he said: "Someone had to explain why they took a decision not to do it, because otherwise it left them looking suspicious and it looked like they'd been leaned on because the BBC wanted to run two specials about Jimmy Savile."
Ten police officers and staff are working on the investigation, dubbed Operation Yewtree, but it is thought their report may take longer than originally expected to be completed.
Dame Janet Smith, who headed the inquiry into the activities of serial killer Harold Shipman, has been appointed to head an inquiry into Savile's time at the BBC.
Scotland Yard said it recognised "her need to progress this important work", adding: "We are now in a position to advise the BBC that they can ask the chair of the BBC executive board Dame Fiona Reynolds to begin her review to run parallel to our investigation. We will develop a protocol to ensure any future potential criminal action is not jeopardised."
It has also emerged the BBC is aiming to produce a special edition of Panorama looking into issues surrounding Jimmy Savile's years of abuse, which could be shown on Monday.
Peter Watt, head of the NSPCC's helpline, said: "We have received more than 136 calls directly relating to allegations against him, which we've passed to the police."