The 27-year-old arrives on a five-year contract, with the option for a further year.
Sterling said it was a “pleasure” to join the Blues and in doing so return to London.
He initially left QPR’s academy as a teenager to join Liverpool.
Sterling told Chelsea’s official website: “First and foremost, it’s a pleasure to be here.
“I’ve obviously achieved a lot in my career so far, but there is still so much more to achieve and I’m really looking forward to doing that in a Chelsea shirt, under Thomas’s management.
