Brittany Ferries has cancelled its services from Cork to Roscoff due to strike action by French crews.
In a statement, Brittany Ferries apologised for the inconvenience and said all passengers had been contacted with alternative arrangements.
Around 300 cars with passengers have been affected by today's cancellations.
The company recommended, via twitter, that passengers on tonight's 9.15pm sailing from Roscoff to Cork travel to Cherbourg where they will be accommodated on alternative sailings to Ireland.
The 4pm Cork to Roscoff sailing is cancelled.
Passengers are asked to visit the company's website for further information.
The cancellations follow those in Portsmouth and Plymouth by the company after two days of strikes.
The UK cancellations are until further notice because of industrial action by some French crew members unhappy with working terms and conditions.
Brittany Ferries came to Cork in 1978 and have up to three sailings a day during the summer months