Werner, 24, will remain with Leipzig until the end of the Bundesliga season. Chelsea stated he'll join his new teammates in July, meaning he won't partake in the remainder of Leipzig's Champions League campaign, which is slated to resume in August.
The deal is subject to the forward passing a medical, which has been delayed due to the travel restrictions amid the COVID-19 pandemic.
"I am delighted to be signing for Chelsea, it is a very proud moment for me to be joining this great club," Werner said. "I of course want to thank RB Leipzig, the club and the fans, for four fantastic years. You will forever be in my heart. I look forward to next season with my new teammates, my new manager, and of course the Chelsea fans. Together we have a very successful future ahead of us."
Werner's in the midst of a career season, with 32 goals and 13 assists in 43 appearances across all competitions; only Robert Lewandowski has more Bundesliga tallies this year.
"We are very excited that Timo Werner has chosen to join Chelsea. He is a player who was coveted all over Europe and it is no surprise, he has that rare mix of being young and exciting and yet established and proven," Chelsea director Marina Granovskaia said.
The Blues beat out the likes of Liverpool and Bayern Munich for Werner's signature. Though Jurgen Klopp is a longstanding admirer of his compatriot, the soon-to-be Premier League champions reportedly never made an official offer despite the mutual admiration between the club and player.
The rising star is the second marquee signing for the west London outfit heading into the 2020-21 season, following February's capture of Hakim Ziyech from Ajax. Werner gives manager Frank Lampard an impressive core of young attacking talent, as the German joins the likes of Tammy Abraham and Christian Pulisic at Stamford Bridge.