The Lachine Rapids are a series of rapids on the Saint Lawrence River, between the Island of Montreal and the south shore. They are located near the borough (formerly city) of Lachine.

In the past these represented a considerable barrier to maritime traffic. Until the construction of the Lachine Canal through Montreal, the rapids had to be portaged. Even with the canal, the difficulty was such that it was usually more convenient to ship goods by rail to Montreal, where they could be loaded at the city's port. Montreal was long a major rail hub and Canada's largest port for that reason.

The Lachine Rapids are now passed by the South Shore Canal (Saint-Lambert and Côte Sainte-Catherine locks) of the Saint Lawrence Seaway.

The rapids contain a number of islands used by migratory birds. Whitewater rafting and jet boat expeditions to the rapids are available in Montreal.