Thorsteinsson and Thorsteinsen are patronymic surnames of Scandinavian origin, meaning son of Thorsteinn. In Old Norse and Icelandic names, Þorsteinsson (anglicised Thorsteinsson) is a patronymic, not a family name. Notable people with the names include:
Thorsteinsson
Björn Thorsteinsson (born 1940), Icelandic chess master Raymond Thorsteinsson, Canadian geologist of the Arctic regions Steingrímur Thorsteinsson (1831–1913), Icelandic poet, author, and translator Thorbjorn Thorsteinsson (died 1158), Orcadian (of Orkney) pirate
Thorsteinsen
Cecilie Thorsteinsen, Norwegian team handball player