Office of the Prime Minister Building, Ottawa

The Office of the Prime Minister and Privy Council building, formerly known as the Langevin Block, is an office building facing Parliament Hill in Ottawa. As the home of the Privy Council Office and Office of the Prime Minister, it is the working headquarters of the executive branch of the Canadian government.

Started in 1884 and completed in 1889, the building was the first federal government office building constructed outside the Parliament Hill precinct. It is built of sandstone obtained from a New Brunswick quarry. It occupies a prominent place on Ottawa's Wellington Street, adjacent to the National War Memorial.

The structure is distinctive in Ottawa for its Second Empire Style design because most government buildings from the period were built in the Gothic Revival style. It was designed by the Chief Dominion Architect Thomas Fuller, who also designed the original Parliament Buildings.

The building is not open for public viewing, but one still appreciates its beauty from the outside.