The Invasion of Lingayen Gulf (Filipino: Paglusob sa Golpo ng Lingayen), 69 January 1945, was an Allied amphibious operation in the Philippines during World War II. In the early morning of 6 January 1945, a large Allied force commanded by Admiral Jesse B. Oldendorf began approaching the shores of Lingayen from Lingayen Gulf, on the island of Luzon. U.S. Navy and Royal Australian Navy warships began bombarding suspected Japanese positions along the coast of Lingayen from their position in Lingayen Gulf for three days. On "S-Day", 9 January, the U.S. 6th Army landed on a roughly 25 mi (40 km) beachhead at the base of the Gulf between the towns of Lingayen and San Fabian.

Sixth Army is a theater army of the United States Army. The Army service component command of United States Southern Command, its area of responsibility includes 31 countries and 15 areas of special sovereignty in Central and South America and the Caribbean. It is headquartered at Fort Sam Houston.

The Sixth Army saw extensive service in the South Pacific during World War II, including in New Britain, New Guinea, and the Philippines. Postwar it served stateside training army forces until its inactivation during force reduction in 1995. The army was reactivated in 2007.