Lac-Mégantic is a town and name of a freshwater lake in Estrie, Quebec, Canada.
Formerly called Megantic, the town of nearly 6,000 people was founded in 1884 after the Canadian Pacific Railway began construction of the final segment in its transcontinental railway linking Montreal with the Atlantic Ocean port of Saint John, New Brunswick. The town derives its name from the adjacent Lac Mégantic, located on the municipality's southern boundary. Although the railway has declined in recent decades, Lac-Mégantic remains an important lumbering and farming centre. Other industries have included a paper-printing plant, a sash-and-door factory, saw mills, and a butter, cheese, and cheese box factory.