West Block, Government building on Parliament Hill, Ottawa, Canada

West Block is a government building on Parliament Hill featuring Gothic Revival style with pointed arches, detailed stone carvings, and tall towers along its limestone exterior. The structure spans multiple stories and contains offices, meeting rooms, and parliamentary chambers used for legislative work.

Construction began in 1859 to designs by Thomas Stent and Augustus Laver, and the building was completed in 1865, three years late. Its first tenants were the postmaster general, the Ministry of Public Works and the Crown lands departments. The Mackenzie Wing and Tower were added in 1878, and the Laurier Tower and link in 1906. Since 28 January 2019 it has housed the interim House of Commons while the Centre Block is renovated.

The West Block appears on the obverse of the Canadian five-dollar bill, where the Mackenzie Tower is depicted. Inside, the former Confederation Room, known as Room 200, was lost during the 2011 renovation that created the interim Commons chamber. The building also holds a branch of the Library of Parliament and preserved pre-Confederation spaces.

The interim House of Commons chamber sits in the covered central courtyard, entered from the building's interior; the Mackenzie Tower's lower section is scaffolded in the photograph. Public access follows parliamentary visiting arrangements rather than a fixed tourist route, and the underground levels and tunnels built during the 2011–2019 renovation connect toward other Parliament Hill buildings.

The West Block appears on the obverse of the Canadian five-dollar bill, where the Mackenzie Tower is the element shown. The tower was added in 1878, one of three that rise above the building, alongside the Laurier Tower of 1906 and the Southwest Tower.