Ortelius, Abraham (ôrtēˈlyəs) [key], 1527–98, Flemish geographer, of German origin. Next to his contemporary Mercator, he is the most renowned of the 16th-century Flemish school of geography. He traveled with Mercator in 1560 and was thus inspired to begin his chief work, Theatrum orbis terrarum (1570), the first modern atlas of the world. The first edition of this atlas contained 53 maps, in part compiled from maps of 87 cartographers; the 1587 edition had 103 maps. Ortelius was made geographer to Philip II of Spain in 1575. He produced a number of other geographic works, such as the Thesaurus geographicus (1587).