Montmagny—L'Islet—Kamouraska—Rivière-du-Loup (French pronunciation: [mɔ̃maɲi lilɛ kamuʁaska ʁivjɛʁ dy lu]; formerly Rivière-du-Loup—Montmagny) is a federal electoral district in Quebec, Canada, that has been represented in the House of Commons of Canada since 2004.

The district includes the Regional County Municipalities of Kamouraska, L'Islet, Montmagny and Rivière-du-Loup.

It is also the most French riding in Canada, by mother tongue, and spoken at home.

The district did not have any boundary changes as a result of the 2012 federal electoral redistribution.

Following the 2022 Canadian federal electoral redistribution, the riding will largely be replaced by Côte-du-Sud—Rivière-du-Loup—Kataskomiq—Témiscouata.