Samuel L. Greitzer (August 10, 1905 – February 22, 1988) was an American mathematician, the founding chairman of the United States of America Mathematical Olympiad, and the publisher of the precollege mathematics journal Arbelos. He also wrote the textbook Geometry Revisited together with H. S. M. Coxeter in 1967.
Born in Russia, Greitzer moved to the United States in 1906, graduated from Stuyvesant High School, received his bachelor's degree in 1927 from City College of New York, and later earned a Ph.D. from Yeshiva University. He held academic positions at Yeshiva University, the Brooklyn Polytechnic Institute, Columbia University, and Rutgers University. He died on February 22, 1988 in Metuchen, New Jersey.