Lester B. Pearson Building, Federal heritage building in Lower Town, Ottawa, Canada

The Lester B. Pearson Building is a late modern office complex with Brutalist influence, designed by the Toronto firm Webb Zerafa Menkes, at 125 Sussex Drive in Ottawa's Lower Town. Its four towers range from 4 to 10 storeys, and three of them are linked from the first to the fifth floor. It houses Global Affairs Canada.

Built between 1968 and 1973, the complex was officially opened on 1 August 1973 by Queen Elizabeth II. It is named after Lester B. Pearson, who served as external affairs minister and later as prime minister, and who received the Nobel Peace Prize. Its nickname, "Fort Pearson", comes from its fortress-like appearance, and the name is often used to refer to Global Affairs Canada itself.

The building's nickname, "Fort Pearson", comes from its fortress-like appearance and is used as a metonym for Global Affairs Canada itself. Lester B. Pearson, after whom it is named, was a former external affairs minister, Nobel Peace Prize laureate and prime minister.

The building underwent a major renovation that began in 2019 and continues to modernize office spaces while improving accessibility throughout the complex. Expect some areas to have limited access during the ongoing work.

The architecture blends Late Modern with Brutalism through dark materials and strong horizontal lines that project stability and authority. This design vocabulary was intentionally chosen to visually express the power of governmental institutions.