Walther Heissig (December 5, 1913 – September 5, 2005) was an Austrian Mongolist.
Heissig was born in Vienna. He studied prehistory, ethnology, historical geography, sinology and Mongolian in Berlin and Vienna, and got his doctoral degree in 1941 in Vienna. Afterwards he traveled to China, worked at the Fu-jen University in Beijing and visited China's Inner Mongolia region. In 1945/46 he had to leave China in an affair about alleged espionage for Japan by German nationals. In 1951 he obtained his habilitation at Göttingen, but, on failing to obtain a position there, he undertook to pursue his second habilitation at the Bonn in 1957. In 1964, he was appointed the Chair of the Central Asian seminar at Bonn University.
His major fields of study were Mongolian history, literature, and also Mongolian maps. He not only made a number of invaluable contributions in the academic field, but also edited several popular books on Mongolian history and culture, for example Ein Volk sucht seine Geschichte. He also published several books on Mongolian epics, proverbs, and folk tales.
He worked extensively on the Epic of King Gesar and other epics circulating in Mongolia. In 1978, he initiated a project for the study of epics. Also, with the help of Heissig, the five-volume series "Folklore mongol" by B. Rinchen was published between 1960–1972, followed by a 13-volume series of epics, Mongolische Epen by Nicholas Poppe. His scientific research work has been acknowledged by elections into various learned societies i.a. he was elected foreign member of the Mongolian Academy of Sciences which is the highest scientific honour in Mongolia.