Yukos is one of the world's largest non-state oil companies, after its merger with Sibneft.
It was acquired in controversial circumstances from the Russian Government during the privatization process of the early 1990s.
Yukos is now an active participant in the Russian political process, making donations across the political spectrum. It is considered that that is the reason why Vladimir Putin sanctioned the high-profile arrest of Yukos CEO Khodorkovsky in October, 2003. Shortly thereafter, on October 31, the Russian government froze ownership of 44% of the companies shares. The reason given was to prevent them from them being sold by a group of major shareholders led by Khodorkovsky.