Gylfi Þór Sigurðsson (Icelandic pronunciation: [ˈcɪlvɪ ˈθouːr̥ ˈsɪːɣʏrðsɔn]; transliterated as Gylfi Thor Sigurdsson; born 8 September 1989) is an Icelandic professional footballer who plays as an attacking midfielder for Besta deild karla club Víkingur Reykjavík and the Iceland national team.
Gylfi began his professional career with Reading in the Championship and in 2010, was sold to TSG Hoffenheim, which was Reading's biggest sale at the time. He was voted Player of the Season for two consecutive seasons: for Reading in 2009–10 and for Hoffenheim in 2010–11. After a season back in English football with Swansea City, he joined Tottenham Hotspur for a reported £8 million transfer fee. In 2014, he moved back to Swansea as part of an exchange for Ben Davies. In 2017, he transferred to Everton for a then club-record transfer fee of £40 million, and remained there for five years. In 2021 he was arrested on suspicion of child sexual offences, and was freed without charge in 2023. He then resumed his career with Lyngby in Denmark and Valur in Iceland.
Gylfi made his debut for Iceland in 2010. He played for the team at their first major tournament, UEFA Euro 2016, where it reached the quarter-finals. He also played at his national team's first ever FIFA World Cup in 2018. As of 9 June 2026, Gylfi has obtained 86 caps and scored 28 goals, making him Iceland's all-time top scorer.
Born in Reykjavík, Gylfi played for hometown side FH before joining Breiðablik and was an Icelandic under-17 international. He had spent time on trial with Preston North End before signing for Reading on an academy scholarship on 1 October 2005. He spent three years playing for the youth and reserve teams. Prior to the 2007–08 season, he and five other youngsters were given professional contracts.
Ahead of the 2008–09 season, Gylfi was assigned the number 34 shirt for Reading. He was an unused substitute in the club's 2–1 away win at Dagenham & Redbridge in the first round of the League Cup on 12 August. Two weeks later, he made his debut in the next round against Luton Town, entering the match as a 59th-minute substitute for James Harper in a 5–1 win at the Madejski Stadium. He scored in Reading's penalty shoot-out loss away to Stoke City in the third round after entering as a substitute.
To gain first-team experience, Gylfi signed for Shrewsbury Town on a one-month loan spell on 16 October. Two days later, he scored on his league debut against AFC Bournemouth in a 4–1 win at the New Meadow. He made a total of six appearances during his time at Shrewsbury, scoring one goal. He returned to his parent club and featured in Reading's 2–0 loss to Cardiff City in the FA Cup third round on 3 January 2009. On 27 February, he joined Crewe Alexandra on an emergency loan move. Two days later, he made his debut against Brighton away, scoring in the 89th minute in a 4–0 win. On 24 March, his loan was extended until the end of the season. He scored two further goals for Crewe, against Milton Keynes Dons and Cheltenham Town respectively, but could not prevent the club's relegation to League Two.
Gylfi scored his first Reading goal against Burton Albion from 35 yards out in a League Cup first round tie at home on 11 August 2009. He scored his first league goal for Reading in a 3–2 defeat at Peterborough United on 19 September 2009. Gylfi was a major contributor in Reading's extraordinary 2009–10 FA Cup run which included wins over Premier League sides Liverpool, Burnley and West Bromwich Albion. On 13 January 2010, in the third round of the FA Cup against Liverpool, he scored a penalty in injury time to make the score 1–1 and force extra time. Reading went on to win the match 2–1. He scored the winning goal in the 87th minute against Burnley in the fourth round. In the fifth round, he scored the winning goal against West Brom for a 3–2 victory in extra time. In April 2010, Gylfi won the Championship Player of the Month Award for March, edging Peter Løvenkrands of Newcastle United, Graham Dorrans of West Brom and Adel Taarabt of Queens Park Rangers, scoring five goals in six matches that month. On 2 May, Gylfi scored against Preston North End in the final match of the season. Before the match, Gylfi was named as the 2009–10 Reading Player of the Season, surpassing Jimmy Kébé and Ryan Bertrand, who finished second and third respectively.
Gylfi finished the season with 20 goals in 44 matches in all competitions. His performances and his young age prompted several Premier League clubs to enquire over his availability, but he committed his future to Reading when he signed a three-year contract in May 2010.
Gylfi scored his first goal of the 2010–11 season in the first match of the season when he "skipped past two players before smashing in a 25-yard equaliser" against Scunthorpe United in a 2–1 home loss. He followed this on 28 August with a short-range chip in the 22nd minute away at Leicester City. The evening after the match, the Icelandic media reported Gylfi was to travel to Germany the following Monday to undergo a medical at TSG Hoffenheim ahead of a transfer. On 31 August, he completed a transfer to 1899 Hoffenheim, with Reading reporting the fee received exceeded their previous club record sale of £6.5 million from the sale of Kevin Doyle.
Gylfi made his debut for TSG Hoffenheim on 10 September 2010, coming on as a substitute with 13 minutes to go in a 2–0 win over Schalke 04. One week later, he scored his first goal for Hoffenheim in a 2–2 draw with 1. FC Kaiserslautern after coming on as a 77th-minute substitute. He scored with his first touch, a 20-yard free-kick that levelled the match. His second goal for the club was another free-kick, from 25 yards out against Mainz 05 in a 4–2 away defeat. He added another two goals to his tally in Hoffenheim's home win against Hannover 96, one of which was from the penalty spot. On 25 May 2011, Gylfi was voted as 1899 Hoffenheim's fans' Player of the Season, despite only starting 13 matches. He finished the season with ten goals and two assists.
During the first half of the 2011–12 season, Gylfi fell out of favour with the club's new manager, making just seven league appearances and was linked with a move away from the club.
On 1 January 2012, it was announced Gylfi would join Premier League club Swansea City on loan for the rest of the season. He made his Premier League debut for Swansea on 15 January, coming on at half-time and setting up the winning goal in a 3–2 win over Arsenal. On 4 February, Gylfi scored his first goal for the club in a 2–1 win against West Bromwich Albion. He also created Swansea's other goal for Danny Graham, taking his tally to three assists in four matches. On 3 March, he scored two goals in a 2–0 victory away at Wigan Athletic, his first from a free-kick. Two weeks later, he scored another brace in a 3–0 away win against Fulham. He scored his next goal at White Hart Lane in his team's 3–1 defeat by Tottenham Hotspur on 1 April.
As a result of his fine form, Gylfi was named the Premier League Player of the Month for March, the first Icelander to win the award. His next goal came in a 3–0 victory over Blackburn Rovers that put the club on 42 points for the season.
On 28 May, Swansea agreed a £6.8 million fee with 1899 Hoffenheim for the permanent transfer of Gylfi, subject to him passing a medical. However, following Swansea manager Brendan Rodgers' move to Liverpool, the deal collapsed, despite Huw Jenkins keeping hope in the deal alight. In 18 Premier League matches during his loan spell for Swansea, Gylfi scored seven goals and added four assists.
On 4 July 2012, Gylfi joined Tottenham Hotspur from 1899 Hoffenheim for a reported £8 million transfer fee. He was the first signing for newly appointed Spurs manager André Villas-Boas. On 18 July, he scored his first goal for the club in a friendly against Stevenage after coming on as a second-half substitute. On 26 September, he scored his first competitive goal for the club in a League Cup third round tie away against Carlisle United, closing the scoring in a 3–0 win.