J. Harleston Parker (1873 - May 5, 1930) was an American architect active in Boston, Massachusetts. Parker was born in Boston, graduated from Harvard University in 1893, then studied architecture at the Massachusetts Institute of Technology and, after a further four years at the École des Beaux-Arts in Paris, took his degree in 1899. In 1900, he formed the firm of Parker & Thomas in Boston with Douglas H. Thomas, Jr., which later in 1907 added Arthur Wallace Rice to become Parker, Thomas & Rice. As head of the firm, he designed many notable buildings and served as chairman of the Boston Art Commission.