Almost a week after announcing he had decided to move to Stamford Bridge, the 21-year-old Belgium international was officially confirmed as a Blues player.
Hazard cost a reported £32million from Lille, which would make him the second most expensive player in Chelsea's history behind Fernando Torres.
The club said in a statement on their official website: "Chelsea Football Club is delighted to announce we have agreed terms with Lille for the transfer of Eden Hazard.
"The 21-year-old Belgian international has agreed personal terms with the club and today passed a medical examination. He will join the club in July when the players return for pre-season training."
Hazard added: "I'm delighted to finally arrive here - it's a wonderful club and I can't wait to get started."