Clausen
Clausen is a Danish patronymic surname, literally meaning child of Claus, Claus being a German form of the Greek Νικόλαος, Nikolaos, (cf. Nicholas), used in Denmark at least since the 16th century. The spelling variant Klausen has identical pronunciation (as does the often interchangeable Claussen). 
The two variants are number 34 and 85 on the top100 of surnames in Denmark. Occurrences of Clausen/Klausen as a surname outside Denmark and Schleswig-Holstein are due to immigration. Immigrants to English-speaking countries sometimes changed the spelling to Clauson.

People
Alden W. Clausen, (1923–2013), American businessman and former President of the World Bank
Alf Clausen (born 1941), American film and television musical composer
Andrea Clausen (born 1959), German stage actress (Burgtheater, Vienna)
Arne Clausen (born 1932), Argentine Methodist Pastor
Casey Clausen (born 1981), American football player
Christopher John Clausen (born 1942), American writer
Claus Clausen (1899-1989), German film actor
Claus Kristian Randolph Clausen (1869–1958), US Navy officer in Spanish–American War.
Claus Lauritz Clausen (1820–1892), pioneer Lutheran minister, military chaplain and politician.
Connie Clausen (1923–1997), US actress, author
Curtis Paul Clausen (1893–1976), American entomologist
Donald Holst Clausen (1923–2015), US politician
Frits Clausen (1893–1947), the leader of the Danish Nazi Party before the Second World War
George Clausen (1852–1944), British painter
Henrik Nicolai Clausen (1793–1877), Danish theologian and statesman
Henry Christian Clausen (1905–1993), American lawyer
Herluf Stenholt Clausen (1921-2002), Danish ichthyologist
Hugh Clausen OBE (1888–1972), British naval armaments engineer
Major General Hugh J. Clausen (1926–2009), Deputy Judge Advocate General of the United States Army
Ian Clausen, American philosopher
Jens Clausen (1891–1969), a Danish-American botanist and geneticist
Jimmy Clausen (born 1987), US football player
John Adam Clausen (1914–1996), American sociologist
John Henry Clausen (1852–1930), farmer
Jørgen Mads Clausen (born 1948), Danish industry magnate
Kasper Klausen (born 1982), Danish footballer
Kristoffer Clausen, Norwegian media personality
Lars Clausen (1935–2010), German sociologist
Mads Clausen (1905–1966), Danish industrialist and father of Jørgen Mads Clausen
Mads Clausen (footballer) (born 1984), Norwegian footballer
Meredith Clausen (born 1942), American architectural historian and professor at University of Washington
Néstor Clausen (born 1962), Argentine footballer
Nicolai Clausen (1911–1943), German U-boat commander
Peter Clausen (nineteenth century, dates unclear), also known as Pedro Cláudio Dinamarquez Clausen and as Peter Claussen, Danish natural history collector
Pit Clausen (born 1962), German politician, mayor of city Bielefeld
Raymond M. Clausen Jr. (1947–2004), United States Marine Corps, Medal of Honor recipient, Vietnam War 31 Jan 1970.
René Clausen (born 1953), American composer
Rick Clausen (born 1982), American football player
Roy Elwood Clausen (1891–1956), American botanist and geneticist
Sally Clausen (born 1945), American educational administrator
Thomas Clausen (mathematician) (1801–1885), Danish mathematician and astronomer
Thomas Clausen (musician) (born 1949), Danish jazz pianist
Thomas Clausen (Louisiana) (1939–2002), American education superintendent, brother of Sally Clausen
Sven Clausen (Danish author, playwright, doctor of law)  (1893-1961)

Places
Clausen, Luxembourg, a quarter in Luxembourg City
Clausen, Germany, a town in Rhineland-Palatinate and site of a former US Army chemical weapons facility

Other
Clausen function, a mathematical function


== References ==