Chelsea and adidas have agreed a new 10-year contract worth £290m to the Europa League champions.
An industry insider with knowledge of the deal confirmed it was worth $45m US dollars a year, or around £290m in total until 2023.
Chelsea chief executive Ron Gourlay said: "We are delighted to extend our partnership until 2023 after a highly successful first seven seasons.
"Both organisations share the same ethos and ambition and the new deal reaffirms adidas' belief in the club's status in world football."
The 2012 Champions League winners and 2013 Europa League champions will bid for further success this term under returning manager Jose Mourinho.
The Blues added in a statement: "This is the biggest deal to date Chelsea FC has signed with a partner and will see the sports brand continue to be the official sponsor and sportswear supplier for the club over the next 10 years.
"The partnership, which began in 2006, has continued to grow during a period of continued success for Chelsea.
"The Blues have won major honours both domestically and in Europe, including being the first London club to win the UEFA Champions League. We have also won the Premier League, four FA Cups, the League Cup and last season, the UEFA Europa League."