Navalny, 47, now faces a transfer to a "special regime" prison colony, the harshest grade in Russia's penal system, with the prospect of staying there until he is in his mid-70s.
Daniel Kholodny, a TV technician who worked for Navalny, was sentenced to eight years in jail in August as part of the same trial.
"For all of us - their colleagues and friends - this is constant pain," Navalny aide Leonid Volkov posted on X, formerly Twitter.
The Kremlin has tried to portray Navalny as politically irrelevant, and Putin makes a point of never speaking his name.
Moscow has cast him as an extremist and, without providing evidence, as a puppet of the U.S. Central Intelligence Agency.
Persons:
Alexei Navalny, Viktor Rogov, Vladimir Putin, Daniel Kholodny, Alexei, Kholodny, Navalny, Leonid Volkov, Putin, Russia's, Nelson Mandela, Vladimir Kara, Murza, PUTIN, scoundrels, Mark Trevelyan, Alexandra Hudson
Organizations:
IK, Navalny, U.S . Central Intelligence Agency, Kremlin, U.S . State Department, European Union, Alexandra Hudson Our, Thomson
Locations:
Vladimir, Navalny, Moscow, Ukraine, Siberia, Melekhovo, Russia, Germany