The O'Neill House Office Building is an office building in Washington, D.C., that houses offices of both the House of Representatives and the Department of Health and Human Services. It is named after former United States Congressman from Massachusetts and Speaker of the United States House of Representatives Thomas P. "Tip" O'Neill Jr. and located at 200 C Street Southwest in the Southwest Federal Center district, at the foot of Capitol Hill.

Thomas Phillip "Tip" O'Neill Jr. was an American Democratic Party politician from Massachusetts who served as the 47th speaker of the United States House of Representatives from 1977 to 1987, the third-longest tenure in history and the longest uninterrupted tenure. He represented northern Boston in the House from 1953 to 1987.