It's impossible to overstate the seismic impact the billionaire has had on English football since June 2003.
The Russian has poured over £2 billion into the club, helping the Blues to 16 trophies and transforming the transfer market in the process.
That's not to say that all of that business has been a success, though.
There have been some astute signings - see Michael Essien and Eden Hazard - but there have also been some flops, not to mention some transfers which were just downright bizarre.
So, as the Chelsea owner marks a special landmark after more than 17 years at the helm, here at GIVEMESPORT we've been reminiscing about Chelsea's most random buys of the Abramovich era - and what happened next.
Asier Del Horno
Mainly remembered for being terrorised by Lionel Messi in the Champions League, Del Horno's £8m transfer didn't prove to be a success. After one just season and 25 appearances, he was sold to Valencia.
Chelsea signed the defender for a fee rising to £4m in 2015. The following day, he wasn't named in their Champions League squad and his only appearance came as a substitute in the League Cup.
Tal Ben Haim
Ben Haim was a solid(ish) centre-back for Bolton Wanderers, but nobody expected him to make the move to west London. The Israeli was obviously signed as a back-up, but injuries to John Terry and Ricardo Carvalho then thrust him into the first team.
Like many Chelsea fans, though, he wasn't overly delighted by the decision to replace Jose Mourinho with Avram Grant. "If I knew Avram Grant was going to be the coach I would have signed for another club," he commented before being fined two weeks' wages and eventually being shipped off to Manchester City.
Who forgot this even happened? The Portuguese international joined from Inter Milan on loan in 2009 but only made five appearances. Quaresma then returned to the San Siro before joining Besiktas.
The Argentine could have been a superb signing on loan from Juventus, but he scored just five goals - two of them coming against Huddersfield. Chelsea opted not to extend the deal and he subsequently followed Maurizio Sarri back to Turin.
Signed from QPR for £10.5m, Remy actually got off to a decent start but only ever scored eight league goals. A loan move to Crystal Palace followed, before he was eventually sold to Las Palmas after three years and just 32 appearances.
Chelsea first signed the Serbian in 2005 for €2m when he was just 16-years-old, but he stayed on loan at OFK Beograd. He then went on loan three more times before Andre Villas-Boas requested that he return to Stamford Bridge. Bizarrely, four years after he had put pen to paper on his initial deal, he still hadn't got a visa or a work permit, so he was only able to play in matches that weren't open to the public. He never made a competitive appearance.
Juan Sebastian Veron
Veron was undoubtedly talented, but Chelsea should have known he'd struggle in England following his stint with Manchester United, who had let him leave for £15m. He didn't fare any better in the capital, making just 14 appearances and then leaving for Inter Milan on loan, and ultimately, Estudiante.
There was a time when this would have been a great signing. Yet despite scoring a penalty on his debut, the ex-wonderkid will go down as one of the biggest flops under Abramovich. The Brazilian made just two appearances and then returned to Corinthians.
There's a good reason Chelsea's number nine shirt was considered to be cursed for a long time, Boulahrouz one of the best examples after signing from Hamburger in 2006 for £8.5m. He was actually a defender and made 13 appearances before joining Sevilla on loan.
Mourinho knew Maniche from their time together at Porto, but that was the only real justification for signing him from Dynamo Moscow on loan in 2006. It was pretty clear things wouldn't work out when he was sent off 17 minutes into his debut - but he did get a Premier League winners' medal! He joined Atletico Madrid soon after.
"If you think I'm good, just wait until you see Fabio Paim,” Cristiano Ronaldo reportedly said when he signed for Manchester United. So perhaps it's easy to see why Luiz Felipe Scolari brought in the Portuguese winger. Unfortunately, Paim only lasted four months and only ever played for the reserves before returning to his homeland with Rio Ave.
A reminder that just because things can be done, it doesn't mean they should. Sidwell was a decent cog in Reading's midfield but couldn't make the step up at Chelsea, making 25 appearances in all competitions before joining Aston Villa.
Such are Abramovich's plentiful resources that we're sure he won't be losing too much sleep over the fate of some of his less successful buys.News Now - Sport News