Lampard, a legend of the London side, was named for the position on Thursday after the departure of Maurizio Sarri.
Lampard emerged as the stand-out candidate to take over at Stamford Bridge, having made a promising start to his managerial career with Championship side Derby County.
The 40-year-old faces a testing first season in charge as Chelsea face up to the prospect of a two-window transfer ban, though they have appealed the decision.
Speaking after his confirmation as a manager, Lampard said: “I am immensely proud to be returning to Chelsea as head coach.
“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.”