Siarhei Tsikhanouski was imprisoned in May last year as he prepared to run for the presidency against Belarus' strongman leader Alexander Lukashenko, the Reuters news agency reported.
Tsikhanouskaya ran in her husband's place in the presidential election. Mass protests broke out in the country after the opposition accused Lukashenko of rigging the vote in August last year.
Tsikhanouskaya confirmed in a tweet on Tuesday that her husband, who denied the charges against him, was "sentenced to 18 years in prison."
Meanwhile, several other Belarusian opposition activists were handed prison terms ranging from 14 to 16 years, Tsikhanouskaya said, listing Artsiom Sakau, Dzmitry Papou, Ihar Losik, Uladzimir Tsyhanovich and Mikalai Statkevich.
"They're repressed for the wish to live in a free Belarus," Tsikhanouskaya tweeted.
Source: Reuters, rp.pl