Pavel Seviarynets was sentenced along with six other activists on Tuesday amid international fury over Minsk's forced diversion of a passenger jet to arrest an opposition journalist.
The leader of an opposition party in Belarus was sentenced to seven years in prison on Tuesday, according to a human rights watchdog.
Pavel Seviarynets, 44, co-founded the Belarusian Christian Democracy party. He was arrested in June last year after a picket in support of opposition presidential candidates.
"On May 25, 2021, Judge Iryna Lanchava of the Mahilioŭ Regional Court sentenced Pavel Seviarynets to seven years in a medium-security penal colony," Viasna Human Rights Center wrote on its website.
Video released on social media on Tuesday showed Severinets chanting "we believe, we can, we will win” shortly after his condemnation. "Belarus will be free," he said.
Severinets was sentenced along with six other activists, journalists present at the hearing told AFP.
All seven have been tried since mid-May in the eastern town of Mogilev for their participation in so-called "mass unrest", a reference to post-election protests last year.
The protest movement began in August 2020 when Alexander Lukashenko claimed his sixth term as president in an election allegedly rigged in his favour.
Lukashenko’s government has harshly repressed post-election protests, the largest of which attracted up to 200,000 people.
More than 30,000 people have been detained since the demonstrations began, with thousands beaten, according to human rights groups.
Tuesday's harsh sentences come as Lukashenko's regime has sparked international fury when a Ryanair flight was forced to land in Minsk on Sunday and a Belarusian journalist on board was detained.
There were 421 political prisoners in Belarus as of Tuesday, according to Viasna Human Rights Center.