Magnúsdóttir is an Icelandic patronymic meaning "daughter of Magnús". In Old Norse and Icelandic names, it is not a family name. Notable people with the surname include:
Agnes Magnúsdóttir (1795–1830), last person to be executed in Iceland Áslaug Magnúsdóttir, Icelandic businesswoman Elín Rósa Magnúsdóttir (born 2002), Icelandic handballer Guðrún Kristín Magnúsdóttir (born 1939), Icelandic author Hólmfríður Magnúsdóttir (born 1984), Icelandic footballer Lilja Rafney Magnúsdóttir (born 1957), Icelandic politician Selma Sól Magnúsdóttir (born 1998), Icelandic footballer Sigrún Magnúsdóttir (born 1944), Icelandic politician Þóra Magnúsdóttir (born c. 1100;), daughter of King Magnus III of Norway Þórunn Elfa Magnúsdóttir (1910–1995), Icelandic writer