Sven Magnus Øen Carlsen (born 30 November 1990) is a Norwegian chess grandmaster. Carlsen is a five-time World Chess Champion, five-time World Rapid Chess Champion, and the reigning (shared with Ian Nepomniachtchi) eight-time World Blitz Chess Champion. He has held the No. 1 position in the FIDE rankings since 1 July 2011, the longest consecutive period of time, and trails only Garry Kasparov in time spent as the highest-rated player in the world. His peak rating of 2882 is the highest in history. He also holds the record for the longest unbeaten streak at the elite level in classical chess at 125 games.

A chess prodigy, Carlsen finished first in the C group of the Corus chess tournament shortly after he turned 13 and earned the title of grandmaster a few months later. At 15, he won the Norwegian Chess Championship, and later became the youngest ever player to qualify for the Candidates Tournament in 2005. At 17, he finished joint first in the top group of Corus. He surpassed a rating of 2800 at 18, the youngest at the time to do so. In 2010, at 19, he reached No. 1 in the FIDE world rankings, the youngest person ever to do so.

Carlsen became World Chess Champion in 2013 by defeating Viswanathan Anand. He retained his title against Anand the following year and won both the 2014 World Rapid Championship and World Blitz Championship, becoming the first player to hold all three titles simultaneously, a feat which he repeated in 2019 and 2022. He defended his classical world title against Sergey Karjakin in 2016, Fabiano Caruana in 2018, and Ian Nepomniachtchi in 2021. Carlsen declined to defend his title in 2023, citing a lack of motivation.

Known for his attacking style as a teenager, Carlsen has since developed into a universal player. He uses a variety of openings to make it harder for opponents to prepare against him and reduce the utility of pre-game computer analysis. Carlsen has stated that the middlegame is his favourite part of the game as it comes down to "pure chess".

Carlsen was born in Tønsberg, Norway, on 30 November 1990 to Sigrun Øen (1963–2024), a chemical engineer, and Henrik Albert Carlsen, an IT consultant. The family spent one year in Espoo, Finland, and then in Brussels, Belgium, before returning to Norway in 1998, where they lived in Lommedalen, Bærum. They later moved to Haslum. Carlsen showed an aptitude for intellectual challenges at a young age. At two years, he could solve 50-piece jigsaw puzzles; at four, he enjoyed assembling Lego sets with instructions intended for children aged 10–14.

His father, a keen amateur chess player, taught him to play at the age of five, although he initially showed little interest in it. Magnus has three sisters; he has said his original motivation to study chess seriously was a desire to be able to beat his elder sister.

Carlsen developed his early chess skills by playing alone. Carlsen had an exceptional memory and could recall the locations, populations, flags and capitals of all the countries in the world by the age of five. He participated in his first tournament—the youngest division of the 1999 Norwegian Chess Championship—at 8 years and 7 months, and scored 6/11.

Carlsen was coached at the Norwegian College of Elite Sport by the country's top player, Grandmaster (GM) Simen Agdestein, who in turn cites Norwegian football manager Egil "Drillo" Olsen as a key inspiration for his coaching strategy. In 2000, Agdestein introduced Carlsen to Torbjørn Ringdal Hansen, a former Norwegian junior champion and later International Master (IM) and GM, as Ringdal served a one-year siviltjeneste (an alternative civilian service programme) at the college.^{[citation needed]}