Speculation was rife last week that Chelsea was set to sign a major contract with either Nike or Adidas to replace Umbro, which the West London club paid £24.5m to get out of its contract five years early.
The deal will be announced officially in the next two days but it is understood the contract will run for 10 years, starting in the summer of 2006.
The £100m deal is a testament to the turnaround in Chelsea's on-pitch and commercial fortunes since Russian billionaire Roman Abramovich took over the club and Peter Kenyon, formerly of Manchester United, was named Chelsea chief executive.
Last night, Chelsea faced Premiership rivals Manchester United at Old Trafford, where Chelsea won 2-1 after Damien Duff scored from a free kick with six minutes remaining. The club is still in with a chance to take home four trophies this season.
It is estimated that the Chelsea's deal with Umbro was worth only £2m a season, while the Adidas deal is understood to be worth more than 10 times that figure.
The deal is one of the biggest in UK football, although not as big as Man Utd's £303m deal with Nike, which also gives the US sports giant control of all merchandising.
Chelsea has not gone that far and retains control of merchandising rights, in a deal that is similar to those Adidas has with Real Madrid and Bayern Munich.
Chelsea is next expected to sign a major shirt sponsor after it parted company with its partner of five years, Emirates Airlines, which dumped the team in favour of a deal with Premiership rivals Arsenal. Emirates swapped teams in a £100m deal with Arsenal that will see the North Londoners' new Ashburton Grove Ground named Emirates Stadium.
Chelsea has been linked with Siemens Mobile as a possible shirt sponsor -- notably Siemens also sponsors Real Madrid, where David Beckham plays. He has been constantly linked to a move to Chelsea.
The deal with Adidas will kick in during 2006 when Chelsea's deal with Umbro finally expires.
For Adidas, the deal comes as it fights to regain its footing in the soccer world against Nike. It follows its $350m (£187.4m) deal with Fifa to sponsor the 2010 and 2014 World Cup tournaments.
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