Hublot's brand will be visible on LED boards and video screens at Chelsea's home ground at Stamford Bridge, plus clocks installed in the stadium.
It isn't clear whether Hublot, like Rotary, will also produce Chelsea FC-branded watches to sell to fans.
Rotary was Chelsea FC's first watch partner, but appears to have opted out of its sponsorship following its acquisition last year. The brand's UK parent company, Dreyfuss, was bought by China Haidian last April.
Switzerland's Hublot, for its part, is strengthening its association with football through the Chelsea deal, having already signed up manager Jose Mourinho (pictured above - no we're not sure what that is on his head either) as ambassador last year. Other faces for the brand include Pele, Scolari and Falcao. Hublot was also official timekeeper at the FIFA World Cup in 2014.
Chelsea FC's managing director, Christian Purslow, said: "As the first luxury brand to invest in football back in 2006, Hublot has an illustrious history and reputation, and shares our values and a commitment to excellence."