Johan-Sebastian Christiansen is a Norwegian chess player who was awarded the title of Grandmaster by the International Chess Federation FIDE in 2018.
Christiansen was born on June 10, 1998 in Norway. He learnt to play chess at the age of nine. His first achievement came in 2014 when he won the Under 16 Norwegian Chess Championship. In 2016 he won the Junior Chess Championship in Norway. He also participated in the 2016 World Junior Chess Championship in Bhubaneswar, India. In 2017, Christiansen received his International Master title after winning the Rilton Cup in Stockholm.