A first half Gylfi Sigurdsson effort proved the difference as Swansea beat 1-0 Chelsea at the Liberty Stadium.
The home side threatened first through the impressive Jefferson Montero but his shot was comfortable for Asmir Begovic.
Montero was also instrumental in the Swans taking the lead in the 25th minute as his cross was only half cleared to Gylfi Sigurdsson, who volleyed home into the bottom corner.
The away side had a great chance to equalise on the stroke of half-time when Oscar picked out fellow Brazilian Pato ten yards out, but the striker somehow managed to blaze over.
Both sides created chances in the second half, with Sigurdsson missing a sitter before Lukasz Fabianski made a decent save from substitute Radamel Falcao’s shot.
The home side held on though and in the process earned their first win over the Blues in the Premier League, who were beaten for the first time in the League since Guus Hiddink took charge.