Harrington Lake (French: La résidence du lac Mousseau) is the summer residence and all-season retreat of the prime minister of Canada, and also the name of the land which surrounds it.

[2] The property includes four recreational buildings; the land, which formerly consisted of cultivated fields, has reverted to secondary forest.

He also ordered the demolition of the mill buildings at Harrington Lake, and replaced them with a 16-room cottage that was designed in the Colonial Revival style, very common in the 1920s according to the NCC, but with the addition of large fieldstone chimneys.

In 1951, the lake and the property (including neighbouring land belonging to William Duncan Herridge and Stanley Healey) were acquired by the King in Right of Canada to build up preserves of natural areas around the capital.

In 1959, supporters of Prime Minister John Diefenbaker suggested that he needed a quiet place to go fishing, not too far from Ottawa.