BEIJING — A Chinese human rights activist who went by the online name “Super Vulgar Butcher” and made public shaming of officials a raucous art form was sent to prison for eight years after a court declared him guilty of subversion on Tuesday after an earlier, secretive trial.

The activist, whose real name is Wu Gan, became renowned among rights advocates for helping organize boisterous protests outside courthouses and government offices to support plaintiffs and defendants who accused officials of abusing their power. Mr. Wu, easily recognized by his shaven head and goatee, relied on social media, a wide and fluid network of online supporters and abrasive mockery to spread his message. He had humorously likened himself to a butcher disposing of foes of human rights.

The verdict underlined how under President Xi Jinping, determined activists like Mr. Wu, who once survived at the edges of official tolerance, have come under concerted attack from the police, prosecutors and courts, with the state news media often acting as a cheerleader.

The court in Tianjin, a port city near Beijing, where Mr. Wu was tried and convicted, said that he had “used ‘rights defense’ and ‘performance art’ as a ploy” to “seriously harm national security and social stability,” said an official summary of the verdict.