Guðmundur Þorsteinsson (1 October 1942 – 16 January 2011) was an Icelandic basketball player and coach. Playing the center position, he was considered one of the best Icelandic basketball players of his generation and was a key player in ÍR's domination of the Icelandic championship in the early sixties. He was forced to retire from basketball at the age of 22 due to a serious illness.