Þorsteinsson is a surname of Icelandic origin, meaning son of Þorsteinn. In Icelandic names, the name is not strictly a surname, but a patronymic. The name may refer to:
Indriði G. Þorsteinsson (1926–2000), Icelandic novelist and short-story writer
Klængur Þorsteinsson (1102–1176), Icelandic Roman Catholic clergyman; bishop of Iceland 1152–76
Magnús Þorsteinsson (contemporary), Icelandic businessman; chairman and boardmember of several large businesses
Pétur Þorsteinsson (born 1955), Icelandic priest and neologist; leader of an Icelandic language movement
Skúli Þórsteinsson (fl. 11th century), Icelandic poet and warrior
