Lebedev, a leader of the Left Front political movement and critic of Russian President Vladimir Putin, pleaded guilty in court. The charges were brought after a pro-government television channel aired secretly taped footage in 2012 of three people, including Lebedev, discussing a plot to topple the government, the Russian news agency RIA-Novosti reported.
The other two people, activists Sergei Udaltsov and Leonid Razvozzhayev, were also charged, and await trial. Each has denied the charges, RIA-Novosti said.
Lebedev was sentenced to 2 1/2 years in prison.