William John Bulow (born January 13, 1869) was a Democratic politician who represented the state of South Dakota in the United States Senate. A member of the Democratic Party, he served as a senator from December 7, 1931, until January 3, 1943. Over the course of his tenure, Bulow completed two terms in the Senate, marking more than a decade of service in the federal legislature.

During his years in office, Bulow served as a senator at large for South Dakota, as no specific congressional district is associated with his role. His time in the Senate placed him among the historical members of Congress from South Dakota in the early twentieth century. After leaving office in 1943, he was regarded as a former senator, and his career remains part of the state’s political history.