Former Chelsea midfielder has been appointed as the new manager of the club where he spent the majority of his playing career.
His successor, Maurizio Sarri, recently left on good terms to join Italian champions Juventus.
Lampard had a successful first season in management, taking Derby to the Championship play-off final. The east-midlands club were narrowly beaten by Aston Villa on the day.
The new Chelsea boss is well known for his long and illustrious career as a player for the blues. He made 648 caps and won 11 major trophies.
Lampard has joined the club at a tumultuous time as they are currently appealing a two-window transfer ban handed to them by Fifa.
“I am immensely proud to be returning to Chelsea as head coach,” said Lampard.
“Everyone knows my love for this club and the history we have shared. However, my sole focus is on the job in hand and preparing for the season ahead.
“I am here to work hard, bring further success to the club and I cannot wait to get started.”
Since buying the club in 2003, Roman Abromovich has now appointed 10 different managers.
“It gives us great pleasure to welcome Frank back to Chelsea as head coach,” said Chelsea director Marina Granovskaia. “Frank possesses fantastic knowledge and understanding of the club.”
Lampard will be joined at the club by assistant manager Jody Morris and first-team coach Chris Jones.
Petr Cech, himself a former Chelsea legend, has also joined the club as a technical advisor.
Lampard’s first major test will come in their season opener against Manchester United on 11 August.