Human rights lawyer Jiang Tianyong, 46, had taken on many high-profile cases, including those of Falun Gong practitioners, Tibetan protesters and victims of the 2008 contaminated milk powder scandal, before being disbarred in 2009.
Jiang sat in court, flanked by two police officers, as a judge handed him the jail sentence and told him he would also be deprived of political rights for three years, according to a video posted on the social media account of the Changsha Intermediate People's Court.
The court accused him of "inciting subversion of state power," and defaming the government, in what Amnesty International has called a sham trial.
"Jiang Tianyong has long been infiltrated and influenced by anti-China forces and gradually formed the idea of overthrowing the existing political system of the country," it said.
The court said he had gone abroad for training on how to accomplish the goal and "applied for financial support from foreign anti-China forces."
In the years leading up to his detention, Jiang had repeatedly met foreign officials and politicians, including high-ranking visitors from the US, to discuss China's human rights situation.
The United Nations Special Rapporteur on extreme poverty and human rights, Philip Alston, has said he feared Jiang's previous disappearance was in part retaliation for the lawyer's assistance to UN experts.
Jiang's family has been unable to contact him since his sudden disappearance last November en route from Beijing to Changsha, where he had gone to inquire about detained human rights lawyer Xie Yang.
Xie was detained in the "709 crackdown" of July 2015, and his claims of being tortured in custody, which Jiang helped to publicise, prompted international concern.
Authorities in that crackdown detained more than 200 people, including lawyers who took on civil rights cases considered sensitive by the ruling Communist Party.
Amnesty International's China researcher William Nee said the "fairly harsh" sentence would have a "chilling effect" on Jiang's fellow human rights lawyers.
