Peter Tatchell, who is scheduled to discuss free speech at Portsmouth Festivities this week, was detained for more than an hour after staging the impromptu demonstration near the Kremlin on Thursday.
He held a poster attacking Russian President Vladimir Putin, which read: ‘Putin fails to act against Chechnya torture of gay people.’
Mr Tatchell was detained near the statue of Marshal Zhukov in a public square, which was busy with football fans ahead of the first game of the World Cup.
He was released on bail and told to appear in court on June 26 to face action for breaching a law around unsanctioned protests of any scale, put in place for the World Cup.
But he was told he could leave the country and on Monday posted an image on Twitter of him on a plane extending two fingers in a peace gesture.
Mr Tatchell said: ‘Job done. Goodbye Moscow.
‘No problem at immigration despite my scheduled court appearance on June 26.
‘It was such a honour to support the heroic Russian LGBT+ activists.’
Mr Tatchell, who has experienced problems in Russia in the past, managed to get into the country using a Fan ID he was issued with after buying a ticket.
He is due to speak at Portsmouth Festivities on Wednesday, giving a talk called You Can’t Say That! It is currently unknown if the talk will go ahead as planned.
The campaigner recently spoke to The Guide about his visit, explaining why free speech is such an important matter.