A judge is putting the public on notice … warning people to stop trying to identify the mystery celebrity fighting to keep serious sexual misconduct allegations under wraps … or they could wind up behind bars themselves.

Judge Matthew Nicklin issued the warning during a hearing in London’s High Court Tuesday … after online sleuths began tossing around names in an attempt to unmask the famous man, who’s only been identified in court as “PPT.”

According to The Independent, the judge acknowledged the growing speculation … but made it clear that even if a name is being widely circulated online, that doesn’t make it fair game to publish.

He warned that reporting restrictions remain in effect … meaning the press and public are barred from identifying the man, including on social media.

And the consequences could be serious … anyone who violates the court order could face contempt proceedings, potentially carrying up to 2 years in prison or a fine.

Nicklin also pointed out that multiple people have already been named in online speculation … reminding everyone that repeating rumors doesn’t make them facts.

As we previously reported, the unnamed celebrity is suing ITN and The Guardian to prevent them from publishing allegations that he used his fame to pursue girls and young women over several years, including an alleged sexual offense. He denies the accusations.

His lawyers have warned publication could put his life at risk … with the court previously hearing he’d attempted suicide twice in recent months and remains seriously ill.

The news outlets are fighting his effort to block their reporting … arguing the allegations are a matter of public interest.

For now, the celebrity’s identity remains protected … and the judge is making sure everyone knows the rules apply to social media sleuths, too.