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
• Jón Dagur Þorsteinsson (born 1998), Icelandic footballer
• 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
• Þorsteinn Þorsteinsson (1880–1979), Icelandic economist and Esperantist
• Þorsteinn Þorsteinsson (athlete) (born 1947), Icelandic athlete who competed in the 800 metres
• Þorsteinn Þorsteinsson (footballer) (born 1964), Icelandic footballer