Five paintings have been taken stolen from Russborough House, the fourth such raid on the collection.
Two of the masterpieces, including one from Rubens, have been stolen in the past. The raid occurred at 6 a.m. and gardaí were alerted when an alarm went off after the thieves broke a window.
A four-wheel jeep which was recovered a short distance away is being examined by the Garda Technical Bureau.
The five stolen paintings are Rubens' Portrait of Dominican Monk and Venus Supplicating Jupiter; Wilem Van Dervelde's The Calm Sea; The Adoration of the Sheppard, Adrien Van Ostade and The Corn Field, Jacob Van Ruisdael.
The collection is valued as "priceless".
Two of the paintings were previously stolen in 1986. The Portrait of a Dominican Monkwas recovered in 1993, The Corn Fieldwas recovered on the same day.
The raid comes just two days after two stolen paintings were recovered by gardaí. Gainsborough's Madame Baccelliand Bernardo Bellotto's View of Florenceare being examined for possible damage following their theft in an armed raid last year.