It brings an end to Ken Bates' 21 year reign at the club, although he will stay on as chairman indefinitely.
36-year old Abramovich is reported to have a personal fortune of over £3.8 billion and has already pledged to make money available to upgrade the club's training facilities, as well buying new players.
Indeed, within 48 hours of Abramovich's takeover we have already been linked with nearly every major player who may (or may not) be available for transfer.
Question marks have been raised against the legibility of Abramovich's fortune, with the most strong protestations coming from former Sports Minister and Chelsea fan Tony Banks.
Is this a good move for the club? Can Abramovich lead us to that elusive Premiership crown? Share your thoughts on the Chelsea-Mad messageboard.