Underbool is a town in the Mallee region of north-west Victoria, Australia. The town is in the Rural City of Mildura local government area and on the Mallee Highway—between Ouyen and the South Australian border – 476 kilometres (296 mi) north west of the state capital, Melbourne. At the 2006 census, Underbool had a population of 217. The town services the grain farmers and graziers in the area. For tourists it provides access to the Pink Lakes in Murray-Sunset National Park.
The town name is thought to come from the German word underbolt given to it by surveyor Dr. Neumayer when he camped there in October 1861.
A post office opened on 15 July 1912 when a regular mail service was provided by the opening of the railway from Ouyen to Murrayville a month earlier.
Underbool Primary School (No. 3819) opened on 5 November 1913, with a purpose-built school building opening in June 1919. A second weatherboard building was built in 1929, and the former Daalko school building moved there in 1967.
With its neighbouring township Walpeup Underbool had a football team (Walpeup-Underbool) in the Mallee Football League until the league folded in 2015. Golfers play at the course of the Underbool Golf Club on Monash Avenue.