Aaron T. Demarest (1841 – July 13, 1908) was an American carriage manufacturer and automobile body manufacturer. He built carriages in New York City for forty-eight years and luxury automobile bodies for six years.

Demarest was born in Nyack, New York in 1841. In 1855 he moved to New York City.^[1] Five years later he started his own business. The business was located on Park Place.^[1]

In 1873 Demarest and his partner bought the carriage manufacturer Lawrence, Bradley and Pardee Company. The factory located at 61-67 Chapel Street in New Haven, Connecticut, grew to almost 200 workmen. In 1915 production of horse carriages stopped altogether and the factory closed.^[2]

Demarest incorporated as A. T. Demarest Company around 1899.^[3]

One source says Demarest died after contracting ptomaine poisoning at a clambake following his grandson's graduation from Yale.^[4] Another source says he had had an stroke and turned over his business to his brother, William R. Demarest and son, Warren G. Demarest. They then ran the business with the firm's secretary, Gabriel C. Chevalier. Demarest died July on 13, 1908, in Greenwich.^[1]