Police dispersed the Slavic Gay Pride event, which was banned by authorities in Moscow, and about 20 activists were taken away.
A spokeswoman for the FO said: “We can confirm that Peter Tatchell has been arrested in Moscow while taking part in a gay pride rally.
“We are in contact with him and are requesting consular access.”
The rally came ahead of the final of the Eurovision Song Contest in Moscow, ITN reports.
MySoCalledGayLife.com reported earlier today:
Police will “strictly” apply the law to an unauthorised gay rights protest expected to take place in Moscow when the Eurovision Song Contest final is held, a top official said today.