Waltham is a village and municipality in the Outaouais region, part of the Pontiac Regional County Municipality, Quebec, Canada. It is located at the mouth of the Noire River, along the north shore of the Ottawa River at Allumette Island.
The municipality consists of the hamlet of Carroll and the village of Waltham, both near the Ottawa River between Chichester and Mansfield-et-Pontefract, about west of Fort-Coulonge. Quebec Route 148 connects Waltham to Allumettes Island and Pembroke, Ontario.
Its territory, with a maximum elevation of just over , is sparsely populated, the majority of the population living along or near the Ottawa River. The northern portion is a vast extended tract of undeveloped land, dotted with lakes, such as Findlay, Landon, Gagnon, and Caughlin, which are popular for fishing.
The name Waltham, mentionned on the Gale and Duberger map of 1795, comes from a place on the River Lea in Essex, England, named Waltham Abbey. In 1849, the Waltham Township was formed. In 1859, it was officially reorganized into a township municipality, also named Waltham, and its first mayor was John T. Coghlan.
In 1869, the Bryson Township was annexed, creating the United Township Municipality of Waltham-et-Bryson. The name Bryson comes from George Bryson Sr. (1813–1900), influential logging merchant, and mayor of Mansfield-et-Pontefract. In 1888, the railroad from Fort-Coulonge to Waltham was completed but not until August 27, 1894, was the railroad opened by the Pontiac Pacific Junction Railway Company. Four years later, in 1898, a post office was established, called Waltham Station.
In 1937, a hydroelectric generating station and dam were built across the Noire River just north of Waltham village, forming a reservoir called Robinson Lake.
In 1997, Waltham-et-Bryson is reorganized into the Municipality of Waltham.
Total private dwellings (excluding seasonal cottages): 153