Portnablagh (Irish: Port na Bláiche, meaning, depending on translation, either 'port of the flowers' or 'harbour of the buttermilk', from the rough seas in the area.) is a small village in County Donegal, Ireland. Portnablagh (also written in English as Port-na-Blagh) is located on Donegal's North West coast, specifically the west side of Sheephaven Bay. It is on the N56 road.

Portnablagh, along with neighbouring Dunfanaghy, is well-known for its beaches and picturesque harbour. It attracts many tourists, mostly from Northern Ireland, every summer.

The small harbour is well protected on 3 sides and has a relatively short slipway which gets frequent use by fishing and pleasure boat owners, particularly during summer months. It provides access for boat owners to a large number of beaches in Sheephaven Bay, many of which are only accessible on foot or by sea.