More than 1.2 million cigarettes have been seized by customs officers at Dublin Port.
The haul of "'Palace" brand cigarettes, which were contained in a number of pallets described as general cargo, had arrived on a ferry from Belgium.
Officers from Revenue's Customs Service believe the seizure has a retail value of 552,000 euro and a potential loss to the exchequer of 326, 290 euro
A spokeswoman said the seizure is part of Revenue's ongoing operations targeting the supply and sale of illegal cigarettes in the shadow economy.
"If businesses or members of the public have any information regarding the smuggling or sale of illegal cigarettes, they can contact Revenue in confidence," she added.