Julien David Le Roy (French pronunciation: [ʒyljɛ̃ david ləʁwa]), also Leroy (6 May 1724 in Paris – 28 January 1803 in Paris) was an 18th-century French architect and archaeologist, who engaged in a rivalry with Britons James Stuart and Nicholas Revett over who would publish the first professional description of the Acropolis of Athens since an early 1682 work by Antoine Desgodetz. Le Roy succeeded in printing his Ruins of the Most Beautiful Monuments of Greece four years ahead of Stuart and Revett.
Stuart and Revett were researching Athens since 1748 but Le Roy had an advantage in accessing the ruins due to good relations between France and the Ottoman Empire. Le Roy's studies, supported by Comte de Caylus and his art circle, recruited the finest engravers and architects to produce illustrations, and became sort of a national project for the pre-revolutionary France. Le Roy spent only three months in Athens (compared to three years taken by Stuart and Revett); he researched Greek monuments in a wide, universal cultural context, comparing them with Roman legacy, and travelled to Constantinople to study the Byzantine development of the Greek tradition.
Le Roy rushed his Les Ruines des plus beaux monuments de la Grèce (Ruins of the Most Beautiful Monuments of Greece) into print in 1758. Stuart and Revett delayed their first volume till 1762 and discouraged their readers by filling it with lesser monuments instead of the expected Parthenon. The delay provided them time to examine Le Roy's book and pinpoint its weaknesses and errors in a bitter critique. Le Roy's success alienated not only the Britons who harshly attacked his book and theories but also Piranesi who considered the Frenchman a threat to his national pride and, worse, means of subsistence.