Koster is the Dutch/German word for sexton or verger, derived from the Latin custos.
Koster is a common surname in the Netherlands, ranking 45th in 2007 (15,898 people). People with the surname "Koster" or "De Koster" include:
Adam de Koster (1586–1643), Flemish painterAdrie Koster (born 1954), Dutch footballerBo Koster, American rock musicianChava Koster, Dutch rabbiChris Koster (born 1964), American politician from MissouriChris Koster (musician), Canadian singer-songwriterCornelis H. A. Koster (1943–2013), Dutch computer scientistDaphne Koster (born 1981), Dutch footballerEmma Koster (born 1984), Australian athleteFred Koster (1905–1979), American baseball playerGeorge F. Koster (1927–2012), American physicist a.o. known for the Slater Koster Tight-Binding methodHans de Koster (1904–1992), Dutch politicianHenry Koster (1905–1988), German-born American film directorHenry Koster (author) (1793–1820), English coffee-grower, explorer, botanist and authorIrene Koster (1921–2012), Dutch swimmerJan Koster (born 1945), Dutch linguistJans Koster (born 1938), Dutch swimmerJohn Jorah Koster (fl. 1990–2000s), American filmmakerJulian Koster (born 1972), American musicianKaren Koster (born 1980), Irish-Dutch television presenterKym Koster (born 1973), Australian rules footballerLaurens Janszoon Koster (c. 1370–1440), Dutch printerLou Koster (1889–1973), Luxembourg musicianMartijn Koster (born c. 1970), Dutch software engineerMartin Koster (born 1950), Dutch writerNick Köster (born 1989), South African rugby union playerR. M. Koster (born 1934), American authorRaph Koster (born 1971), American computer entrepreneurSamuel W. Koster (1919–2006), American army officer