Seymour B. Durst (c. 1913 – May 15, 1995) was a New York real estate investor and developer. He was also a philanthropist and the inventor of the National Debt Clock.

Durst was born in New York City. He attended the Horace Mann School. He went on to study at the University of Southern California, where he earned a BA in accounting in 1935.

In 1940, Durst joined the real estate firm, the Durst Organization, which had been founded by his father, Joseph. After Joseph's death in 1974, Seymour took control of the Durst Organization. The company invested in Manhattan real estate, based upon Durst's belief that one should never buy anything one cannot walk to.