Sentencing Stephen Gough, judge Sarah Munro QC said: "This is a much more serious offence than the other public order offences. In those circumstances I take the view only a substantial custodial sentence is appropriate."
She said that Gough, who has been on remand, will be eligible for release on August 14 - one day after there is a hearing at Southampton Magistrates' Court to impose a full Asbo on the former Royal Marine.
The judge conceded that, if she had allowed Gough to leave by imposing a sentence commensurate with his time already served: "There is a reality here that he will walk out on these steps naked. I do not think I can ignore that reality.
A man from Hampshire has been jailed for 11 months after being found guilty of breaching an anti-social behaviour order banning him from being naked in public, minutes after it was issued. Stephen Gough, 53, from Eastleigh was not allowed in court for his trial after he refused to wear any clothes.
He had denied the charge but offered no defence at Portsmouth Crown Court.
Simon Jones, prosecuting, said the naked rights activist left Southampton Magistrates' Court on February 28 after being handed the interim order and walked, wearing just his boots and socks, to the road where he was arrested.