William Joseph Walsh (born December 27, 1961) is an American politician, talk radio host, former social worker, and former 2020 Republican Party presidential candidate, who served one term in the United States House of Representatives representing Illinois's 8th congressional district.

Born and raised in the Chicago metropolitan area, Walsh began his career as a social worker providing education and job skills training to students in low-income areas, gradually becoming more politically active. Walsh had unsuccessfully campaigned for Congress in 1996 and the Illinois House of Representatives in 1998, but was elected to the U.S. House in 2010, defeating three-term incumbent Melissa Bean. Though he received little Republican Party support in his bid against Bean, he was popular with the Tea Party movement. In the 1990s, he identified as a moderate Republican, but he later became a conservative and a Tea Party activist.