His former business partner Platon Lebedev likewise faces a new prison sentence, correspondents report.
"Khodorkovsky and Lebedev may only be reformed if they are isolated from society," the judge's verdict says.
The two men were convicted of fraud on Monday but the reading of the 800-page verdict has still to be completed.
Khodorkovsky, once Russia's wealthiest man and seen as a threat to former President Vladimir Putin, was found guilty along with Lebedev of stealing from their own oil firm, Yukos, and laundering the proceeds.
The two men were first arrested in 2003 and sentenced in 2005 for fraud and tax evasion.
Judge Viktor Danilkin has been reading the verdict out since Monday.
After Washington accused Russia of applying selective justice against Khodorkovsky and Lebedev, the Kremlin effectively said the outside world should mind its own business.