Jón Arnór Stefánsson (born September 21, 1982) is an Icelandic professional basketball player who plays for KR of the Domino's League, and a former member of the Icelandic national team.
He won the FIBA EuroCup title in 2005 with Dynamo Saint Petersburg.
He was a member of the NBA's Dallas Mavericks from 2003 to 2004, but he spent the whole season on the injury list and never played a regular season or playoff game with them.On April 30, 2017, he won the Icelandic championship for the third time with KR and was named the 2017 playoffs MVP.
On April 28, 2018, Jón Arnór won his fourth Icelandic championship after KR defeated Tindastóll in the Úrvalsdeild finals.
In November 2018, Jón announced that he would retire after the 2018-2019 season.On 4 May 2019 he won his 5th national championship after KR beat ÍR in the Úrvalsdeild finals 3-2.