Leonard Walter Jerome born November 3, 1817 in Pompey, New York, United States – died March 3, 1891 at Brighton, England , was a Brooklyn, New York entrepreneur and grandfather of Sir Winston Churchill.

Born on a farm, Leonard Jerome grew up to study law and after graduating university, set up practice in Rochester, New York. He later moved to New York City where he became a notable and flamboyant stock market speculator and promoter.

Leonard Jerome acquired a majority shareholder of the New York Times newspaper and had interest in a number of railway companies. A patron of the arts, he was the founder of the American Academy of Music. Jerome was also an avid sportsman and enjoyed yachting with his friend, William Kissam Vanderbilt, but he had a special passion for thoroughbred horse racing. He helped establish the American Jockey Club and built the Jerome Park Racetrack in the Bronx in conjunction with financier August Belmont, Sr. where the first Belmont Stakes was held in 1867. A resident of Brooklyn, he was also responsible for the construction of the Sheepshead Bay racetrack which hosted meets for the Coney Island Jockey Club.

In 1849, he married Clara Hall (1825-1895) with whom he had three daughters, one of whom was Jennie Jerome. Leonard Jerome's wealth afforded his daughters the opportunity to spend much time in Europe where they associated with the aristocratic elite of the day. On the Isle of Wight, Jennie Jerome met and later married England's Lord Randolph Churchill, son of the Duke of Marlborough. They gave Leonard Jerome two grandsons, including Winston Churchill who became Prime Minister of the United Kingdom.

Jerome Avenue in Brooklyn is named in Leonard Jerome's memory, as is Jerome Avenue in the Bronx. In the Bronx, Jerome Park was once the site of a horse racing track. The New York Metropolitan Transit Administration's #4 Train, the Lexington Avenue-Jerome Avenue Express, runs past one of New York's famous landmarks, Yankee Stadium, located between Jerome Avenue and River Avenue at 161st Street.

Leonard Jerome died at the age of 73 in Brighton, England. His body was brought home for interrment in the Green-Wood Cemetery in Brooklyn.