Ken Sema

Early career

Sema got promoted to the IFK Norrköping first team as a 19-year old in 2013. However, he spent the entire season on loan to IF Sylvia and did not get his contract renewed after it expired at the end of the season. In 2014, he signed for second-tier team Ljungskile SK.

Östersunds FK

In January 2016, Sema signed for Östersunds FK in the Allsvenskan, where he would have his major breakthrough. Sema won the 2016–17 Svenska Cupen with Östersund, assisting three of their four goals in the final, and later played a major role in their 2017–18 UEFA Europa League campaign. On 22 February 2018, Sema scored a goal in a 2–1 win against Arsenal in the round of 32. Despite this, Östersund were eliminated from the Europa League after losing 2–4 on aggregate.

Watford

On 4 July 2018, Östersunds FK chairman Daniel Kindberg revealed that Sema was close to signing for Premier League club Watford on a five-year contract. The next day, Watford confirmed the signing. He scored his first goal against Bournemouth on 2 January 2019 in a 3–3 draw. He was integral in helping Watford get promoted back to the Premier League in the 2020–21 season, registering six goals and adding a further six assists. On 6 February 2024, Sema made his 150th appearance for Watford in their FA Cup fourth round replay defeat to Southampton. On 29 January 2025, Sema departed Watford having had his contract terminated by mutual consent.

Loan to Udinese

On 22 August 2019,…

In 2016, Sema was a part of the Sweden Olympic team that played in Brazil, and scored his first U23 goal in a match against South Korea Olympic. In January 2017, he debuted for the Sweden senior team in a friendly 6–0 win over Slovakia. Sema was an unused substitute in the two-legged playoff against Italy in November 2017, which Sweden won, and therefore qualified for the 2018 FIFA World Cup. Despite featuring in commercials with the rest of the Sweden squad before the World Cup, Sema was eventually left out of the World Cup squad. Sema made his competitive international debut in a UEFA Euro 2020 qualifying game against the Faroe Islands national football team which Sweden won 3–0. He was part of Sweden's squad at UEFA Euro 2020 that reached the round of 16 before being eliminated by Ukraine. On 15 June 2025 he scored a hat-trick in an international friendly against Algeria which Sweden won 4–3.

Sema is known for his hard work, a trait that has made him very popular with Watford fans. He likes to dribble past opponents to get into good crossing positions. He is mainly a winger but has occasionally been used at left back or wing back, due to his ability to work hard and track back defensively. He is affectionately known as King Ken by Watford fans.

Sema was born in Sweden to Congolese parents, and his brother Maic Sema is also a footballer. He speaks with a stammer, and after a video went viral of him doing a post match interview with Watford TV, he was praised as a role model for children and adults with speech impediments.