William Zeckendorf Jr. was an American real estate developer. Son of William Zeckendorf Sr., he was the second of three generations of one of New York's great real estate dynasties. While keeping a lower profile than his famously flamboyant father, Zeckendorf Jr. was highly successful in his own right. Like his father, he became known for large-scale projects that transformed neighborhoods.

William Zeckendorf Sr. was a prominent American real estate developer. Through his development company Webb and Knapp — for which he began working in 1938 and which he purchased in 1949 — he developed a significant portion of the New York City urban landscape. Architects I. M. Pei and Le Corbusier designed structures for Zeckendorf's development projects.