Gustavus Wynne Cook was an American banker, businessman, and amateur astronomer. Cook was born in Philadelphia, Pennsylvania, the son of Lavinia Borden and Richard Yerkes Cook. He married Nannie Mumford Bright and they lived at Roslyn House in Wynnewood, Pennsylvania. The Roslyn House Observatory was in their home. They had two daughters, Nancy Wynne Cook Putnam (1897–1980) and Lavinia Cook Wright.