Greencastle (Irish: An Caisleán Nua, meaning 'New Castle')[2] is a commercial fishing port located in the north-east of the Inishowen Peninsula on the north coast of County Donegal in Ulster, Ireland.

Nowadays, given the decline in the fishing industry, it resembles more closely a 'typical' Donegal holiday village.

The port was the fastest growing urban area in County Donegal between the 2016 and 2022 census, with a population increase of 52.6% from 831 to 1,268.

Due to the tidal nature of the Foyle Estuary, it is sometimes too shallow for cruise ships to make their way to Lisahally docks in Derry.

The NFC recently completed a €1.1 million extension funded under the INTERREG 11 Initiative, thus providing better facilities including a realistic simulator bridge deck.