Two men have been arrested following the seizure of 350kg of cocaine, which could be worth over €200m.
The seizures took place in the Blanchardstown and Tallaght areas of Dublin.
It is thought the haul is the largest on land seizure of drugs in the history of the State.
The joint operation was carried out this morning by the Garda National Drugs Unit and supported by officers from the Revenue Customs Service.
A 42-year-old Nigerian man was arrested in the Tallaght area and 50kg of cocaine and a vehicle were seized.
During a follow-up operation in Dublin and Kildare, a 31-year-old Irish man was arrested.
Over 300kg of cocaine was seized in the second seizure in Blanchardstown.
Both men are being held at Clondalkin Garda Station.
Garda Commissioner Martin Callinan said the record seizure is a very significant day for law enforcement in Ireland.
He said investigators have been working on the case for several months.
Speaking to the media in Dublin, Commissioner Callinan said the two men in custody are very significant people in terms of the criminality they have been involved in.
Mr Callinan also said gardaí believe the organised crime group behind the operation is both indigenous and external.
The people involved will have lost a considerable amount in terms of the investment they put into the shipment, he added.
He said that gardaí would be dealing with European and international partners to try to discover where the drugs came from.