August Belmont, Sr. (December 8, 1816 – November 24, 1890) was born in Alzei, Prussia . He immigrated to New York in 1837 after becoming the American representative of the Rothschild family's banking house in Frankfort. On receiving his American citizenship, he married Caroline Perry, daughter of Commodore Matthew Perry.

In 1844, Belmont was named the consul-general of Austria at New York. He resigned in 1850 in response to what he viewed as Austria's cruel treatment of Hungary. In the years following, he served as charg d'affaires for the United States at the Hague, as well as the American minister at the same place. As a delegate to the Democratic Convention in 1860, he supported Stephen A. Douglas. He was named the Chairman of the National Democratic Committee the same year in Baltimore, and held this position until his death in 1872.

An avid sportsman, the famed Belmont Stakes thoroughbred horse race is named for him.

One of his sons was August Belmont, Jr.