Otto the Merry (born July 23, 1301, Vienna; died February 17, 1339, Neuberg an der Mürz ) was a Duke of Austria and the youngest son of Emperor Albert I..

He had two brothers, namely Frederick the Handsome and Albert II. From 1330 onwards, he ruled jointly with Albert.

After the death of Henry of Carinthia, Emperor Louis the Bavarian gave Carinthia and the southern part of the Tyrol as an imperial fief on May 2, 1335 in Linz. Otto was inthronized as duke in accordance with the old Carinthian rite on the Zollfeld , and, from that time onwards, took care rather of Carinthia than of the Duchy of Austria. He founded the monastary of Neuberg an der Mürz in Styria and the Chapel of Saint George in the Augustine Church in Vienna. In February of 1335, he married Anna, the sister of Emperor Charles IV in Znojmo. In 1337 he founded the knightly order Societas Templois for the crusade against the pagan Prussians and Lithuanians. His surname the Merry refers to the festive life at court.