George C. Boldt Yacht House is an historic yacht house located on the northeast shore of Wellesley Island near Alexandria Bay in Jefferson County, New York. It was commissioned by George Boldt to house the many watercraft he owned and is adjacent to Boldt Castle. The yacht house was designed by the Philadelphia architects G. W. & W. D. Hewitt and built in 1903. It is a massive, eclectic, Shingle-style structure composed of five elements, which are: