De Geer (also: De Geer van Jutphaas and De Geer van Oudegein) is a family of Walloon family that belongs to the Swedish and Dutch nobility.
The name is possibly derived from the town of Geer near Liège) . The family moved became notable in Sweden and the Netherlands from the early 17th century, mainly centered on the iron foundry company town Finspång, but often extending to science, art and national politics. The family retained its contacts with the Netherlands even after the main branch settled in Sweden. Some of them hold the title count or baron. Both branches are still in existence and continue to thrive.
- Louis De Geer (1587–1652), financier and industrialist, founder of the Swedish branch.
- Louis De Geer (1622–1695), industrial entrepreneur
- Charles De Geer (1720–1778), Swedish entomologist.
- Charlotta Aurora De Geer (1779-1834), salonist.
- Robert Willem De Geer, lantmarskalk of the Noble estate at the Diet of Porvoo.
- Carl De Geer, lantmarskalk of the Riksdag of the Estates (1823, 1828-1830)
- Louis Gerhard De Geer (1818–1896), Swedish statesman and writer, Prime Minister of Sweden 1876–80
- Karl Vilhelm Konstantin De Geer (1839-1904), Finnish general in the Imperial Russian army 
- Gerhard Louis De Geer (1854–1935), baron, Prime Minister of Sweden 1920–21
- Gerard De Geer (1858–1943), Swedish geologist.
- Sten De Geer (1886-1933), Swedish geographer and ethnographer
- Dirk Jan de Geer (1870–1960), prime minister of the Netherlands.
- Willem De Geer (1927-1984), Swedish artist and portrait painter. Great-grandson of Louis Gerard De Geer.
- Carl Johan De Geer (1938-), Swedish artist.
- Lars-Erik De Geer (1945-), Swedish nuclear physicist.
- Boudewijn de Geer (1955-), Dutch football player, grandson of Dirk Jan de Geer.
- Jonas De Geer (1971-), Swedish nationalist and traditionalist Catholic writer.
- Mike de Geer (1989-), Dutch football player, son of Boudewijn de Geer.
- Nederland's Adelsboek 83 (1993), pp. 42-86.