Austrian architect whose planning of private residences strongly influenced European Modernist architects after World War I. Frank Lloyd Wright (Wright, Frank Lloyd) credited Loos with doing for European architecture what Wright was doing in the United States.

Educated in Dresden, Ger., Loos practiced in Vienna, although he spent extended periods in the United States (1893–97) and in Paris (1924–28). Loos was opposed to both Art Nouveau and Beaux-Arts historicism, and as early as 1898 he announced his intention to avoid the use of unnecessary ornament. His first building, the Villa Karma, Clarens, near Montreux, Switz. (1904–06), was notable for its geometric simplicity. It was followed by the Steiner House, Vienna (1910), which has been referred to by some architectural historians as the first completely modern dwelling; the main (rear) facade is a symmetrical, skillfully balanced composition of rectangles. His essays from this period, denouncing ornament and decoration, were equally influential. Loos's best-known large structure is the Goldman and Salatsch Building, Vienna (1910), in which a little classical exterior detail is offset by large areas of blank, polished marble. A resident of France from 1922, he built a house in Paris for the Dada writer Tristan Tzara in 1926.