The England international will become the first signing at Stamford Bridge since Chelsea's takeover by American magnate Todd Boehly and his consortium.
The Blues splashed out £47.5million on the Manchester City forward as manager Thomas Tuchel looks to bolster his offensive options ahead of the new season.
In a post on social media, Sterling paid tribute to the Citizens, saying: "Seven seasons. Eleven major trophies. A lifetime of memories.
"To the coaching staff who have played a massive role in my development over the years. To my team-mates who have become more than just those I share a pitch with.
"To the backroom staff. To the office staff. To the fans who have tirelessly supported the team, and to everyone involved with Manchester City. My respect for you couldn't be greater.
"What a ride it's been. I am thankful for the ups and the downs, as it's the downs that have, at times, tested my strength and resolve and enabled me to stand here in front of you as the best possible version of myself.
"I arrived in Manchester a 20-year-old. Today I leave as a man. Thank you for your endless support. It's been an honour to wear the shirt of Manchester City."
Sterling moved from Liverpool to Man City in 2015 and has since gone on to make 339 appearances for the club.
The England star has also scored 131 goals during seven seasons of near continuous success with the Sky Blues.
Sterling claimed four Premier League titles, one FA Cup and four League Cups during his time at the Etihad.
However, the one honour eluding him is the Champions League crown, having lost the 2020/21 final against his future employers, Chelsea.