Born in Würzburg, Wien was the son of university professor Wilhelm Wien, and became a lecturer himself in the geography department of Munich University. His mountaineering career began in the Alps, where with Willi Welzenbach he made the first ascent of the north face of the Grossglockner. Outside Europe he made a number of visits to Africa and the Himalaya, including Paul Bauer's 1931 attempt on Kangchenjunga, and a 1936 expedition to Sikkim during which he made the first ascent of Siniolchu.