Plougasnou (; ) is a commune in the Finistère department in Brittany in northwestern France, located about 75 kilometres east of Brest. Plougasnou is northeast of the town of Plouezoc'h, north of Lanmeur and west of Saint-Jean-du-Doigt.
Inhabitants of Plougasnou are called Plouganistes in French.
Plougasnou has been twinned with Helston since 2010.