Ivan Morton Niven (October 25, 1915 – May 9, 1999) was Canadian-American mathematician. He was a member of the University of Oregon faculty from 1947 to his retirement in 1981. He received the University of Oregon's Charles E. Johnson Award in 1981. He was a graduate of the University of British Columbia in his undergraduate studies and was awarded his doctorate from the University of Chicago.
He worked mainly in number theory and completed the proof of Waring's problem in 1944. This conjecture, formulated in 1770, states that every positive integer is the sum of a finite number of nth powers of integers, where the number of powers in the sum depends only on n.
He was president of the Mathematics Association of America (MAA) from 1983 to 1994. He received the MAA Distinguished Service Award in 1989.
He died in 1999 in Eugene, Oregon.
Niven numbers and Niven's constant are named in his honor; also, in 2000, the asteroid (12513) Niven, discovered in 1998, was named after him.