The team announced the move on Wednesday:
Helen Mayo of Everton's PR department tweeted a photo of Lukaku with manager Roberto Martinez:
The Daily Mail's David Kent reports the deal is worth £25 million and will net the Belgium international £75,000 per week.
Lukaku made the move to Stamford Bridge in the summer of 2011. Since then, he's been loaned out on multiple occasions and barely been afforded a chance to prove himself in Chelsea blue.
That situation appeared unlikely to change with Didier Drogba, Fernando Torres and Diego Costa in the squad for the 2014-15 season, so he has decided to kick-start his career elsewhere:
Despite the logjam up front, the decision for Chelsea to sell the youngster still raises eyebrows.
In his two loan spells with West Brom and Everton, the young star scored a combined 32 goals in 66 league appearances. His success ran in an ironic contrast to the struggles of the forwards Chelsea opted to keep instead.
Goalscoring was the Blues' biggest issue last season. On more than one occasion, many supporters asked the question: If manager Jose Mourinho hadn't loaned out Lukaku, would Chelsea be top of the table?
In order to try and remedy the problem, the Blues decided to spend £32 million on Costa, so once again, Lukaku found himself looking at a more established striker likely to be considered ahead of him in the starting XI.
"The Special One" admitted in May that the Belgian had done well at Goodison Park but refused to make any sort of commitment about giving him an important role at Stamford Bridge, per The Guardian's Dominic Fifield:
Lukaku had a successful loan. By that I mean sometimes the players go on loan and we cannot find a positive reason for that loan at the end of the season. But Lukaku played all the time, had minutes of experience in the Premier League in a good team with a good coach, scoring his goals. So he's a successful case of loans and those are the ones we have to analyse. But I haven't discussed [his future] with the player or with my own club yet.
Mourinho has been down this road before, though. Last summer, he made it clear that Juan Mata and David Luiz weren't going anywhere. Then, Mata was sold to Manchester United in the January transfer window, while Luiz's move to Paris Saint-Germain was confirmed at the start of the summer.
The Chelsea manager is famous for his mind games, so it's always hard to tell when he's being genuine and when he's only trying to drive the transfer fee up.
Everton will be delighted to have gotten their man. Martinez built a frightening attack around Lukaku last term, combining his power with the speed of Kevin Mirallas and the invention of Ross Barkley.
The Times' Tony Barrett claims Lukaku was Martinez's No. 1 target of the summer:
Getting a player of Lukaku's calibre, ahead of his prime years, is certainly a coup for the Toffees. There's no question that Chelsea's loss is Everton's gain.
Lukaku is one of the best young strikers in Europe, and it's easy to forget he just turned 21 in May. Daniel Storey of Sky Sports pointed out how many first-team appearances he's racked up compared to some of the more promising players of the last few years:
According to WhoScored.com, no other player under the age of 21 had more combined assists and goals:
While the Belgian still has some kinks to work out in his game, he's much more advanced as a player than many other stars his age. He won't even hit his peak for another four or five years, and that's scary.
What Lukaku does so well is take advantage of defences that are tiring in the second half. He's such a physical presence that he can bully almost any other centre-back, and his combination of speed and power is all the more valuable late in games.
Look at how many of his goals from 2013-14 came in the second half, per Opta:
He wasn't some sort of flat-track bully, either:
Chelsea may regret letting such a talented young striker go before he actually had any opportunity to feature in the first team, but the London club could get him back at some point. This could be similar to when the Blues let Nemanja Matic go to Benfica and ended up buying him back for a €25 million fee.
Meanwhile, Everton have found the man who could potentially be their No. 10 for the next decade.