American novelist and banker whose posthumously published novel David Harum: A Story of American Life (1898) was immensely popular.

Westcott attended schools in Syracuse until age 16, when he became a junior clerk in a local bank. He devoted the next 30 years of his life to the banking business. In the summer of 1895 Westcott began to write David Harum while recuperating in the Adirondack Mountains from tuberculosis. He continued writing the book in Italy and finished it in late 1896 after returning to the United States. The book was rejected by six publishers before it was finally accepted for publication late in 1897.

Westcott died in March 1898, six months before the publication of David Harum, which became a best-seller. More than 1,000,000 copies of the book were sold in the next four decades. David Harum is the story of a shrewd, crusty small-town banker in upstate New York who has an abundant fund of humour, an obvious talent for horse trading, and a strong streak of Yankee decency. A dramatization of the book in 1900 provided the American comic actor William H. Crane with one of his finest roles. Crane and later Will Rogers appeared in respective motion-picture versions of the story.