Donald Arvid Nelson is an American former professional basketball player and head coach. Nelson is second all-time in regular season wins of any coach in NBA history, with 1,335 (a record he held for nearly 12 years). During his career he coached the Milwaukee Bucks, the New York Knicks, the Dallas Mavericks, and the Golden State Warriors. After an All-American career at the University of Iowa, Nelson won five NBA championships playing with the Boston Celtics, with his number 19 retired by the franchise in 1978.