Remy appeared set to join Liverpool in July, only for Brendan Rodgers' side to pull the plug on the deal amid reports of the 27-year-old failing a medical.
However, that has not dissuaded Chelsea from making a move for a player who scored 14 Premier League goals in 26 appearances when on loan at Newcastle United last season.
Having agreed to let Fernando Torres move to Milan on a two-year loan, Chelsea were keen to bring in an additional centre-forward to compete with Diego Costa and Didier Drogba.
And Remy has penned a four-year deal at Stamford Bridge.
"I feel very happy and very proud," said the forward.
"When I heard Chelsea wanted to sign me I said 'let's go' straight away because they are one of the best clubs in the world.
"I remember the amazing atmosphere at Stamford Bridge when I played there for Marseille and I can't wait to play for the first time in front of my new fans."
Remy played 16 games in total for QPR, netting six goals.
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