Otto Koloman Wagner (July 13, 1841 – April 11, 1918) is an Austrian architect and urban planner.

He is a leading member of the Vienna Secession movement of architecture, founded in 1897, and the broader Art Nouveau movement.

All of his works are found in his native city of Vienna, and illustrate the rapid evolution of architecture during the period.

His early works are inspired by classical architecture

By mid-1890s, he had already designed several buildings in what becomes known as the Vienna Secession style.

Beginning in 1898, with his designs of Vienna Metro stations, his style becomes floral and Art Nouveau, with decoration by Koloman Moser.

His later works, 1906 until his death in 1918, have geometric forms and minimal ornament, clearly expressing their function.

They are considered predecessors to modern architecture.