The Swans' Icelandic midfielder has signed on at The Liberty Stadium until 2020.
Sigurdsson enjoying second spell in Wales
Since returning to Swansea in 2014 after a difficult spell in North London with Tottenham Hotspur, Sigurdsson has enjoyed a resurgent spell in South Wales.
Originally on loan from Bundesliga side Hoffenheim in January 2012, The Icelandic scored seven goals and assisted five times up until May.
Amassing 10 assists in just half a season, his form led to Swansea agreeing a £6.8m fee with the Germans for the permanent transfer of Sigurdsson. After Brendan Rodgers moved to Liverpool however, the move was thrown into doubt.
Swansea chairman Huw Jenkins hoped a deal could still be reached but Spurs swooped and new boss Andre Vilas-Boas made the midfielder his first signing for £8.8m.
During his two years at White Hart Lane however, Sigurdsson suffered indifferent form scoring just eight goals in two seasons. That led to a return to Wales where the midfielder took no time in picking up his prolific form, scoring 18 goals since his return, with 11 last term, despite the departure of Garry Monk and the arrival of Francesco Guidolin.
Midfielder creative force for Swans
Sigurdsson continued to be a hugely creative influence from both set-pieces and long-range for Swansea, with 14 assists in 68 apperances.
Speaking via social media the Icelandic said he was, “Delighted to have signed a new 4 year deal with @swansofficial" and that he was "looking forward to the new season.”
Swansea city begin their 2016/17 campaign on August 13 away to newly-promoted Burnley at Turf Moor.