The Naval Service Vessel LÉ William Butler Yeats (P63) has detained a French registered fishing vessel approximately 45 nautical miles south-west of Mizen Head.
A spokesperson for the Defence Forces said that the detention was in relation to alleged breaches of fishing regulations.
The vessel is being escorted to Castletownbere, where it will be handed over to An Garda Síochána.
This is the twelfth vessel detained by the Naval Service in 2020.
The Defence Forces conducts at sea fishery inspections in line with the service level agreement with the Sea Fishery Protection Authority, as part of its delivery of government services to the state.