Igor de Rachewiltz (April 11, 1929 – July 30, 2016) was an Italian historian and philologist specializing in Mongol studies. He was born in Rome. In 1947, he read Michael Prawdin's Tschingis-Chan und seine Erben ("Genghis Khan and his Heritage") and became interested in learning the Mongolian language. He graduated with a law degree from a university in Rome and pursued Oriental studies in Naples.

In the early 1950s, de Rachewiltz went to Australia on scholarship. He earned his PhD in Chinese history from Australian National University, Canberra, in 1961. His dissertation was on Genghis Khan's secretary, 13th-century Khitan scholar Yelü Chucai. He married Ines Adelaide Brasch in 1956 with whom he had one daughter.

In 1965 he became a fellow at the Department of Far Eastern History, Australian National University (1965–67), becoming a senior Fellow of the Division of Pacific and Asian History at the Australian National University (1967–94), a research-only fellowship. He published a translation of the Secret History of the Mongols in eleven volumes of Papers on Far Eastern History (1971–1985). He also completed projects by the prominent Mongolists, Antoine Mostaert and Henri Serruys, after their deaths. He became a visiting professor at the Sapienza University of Rome three times (1996, 1999, 2001).

In 2004, he published his translation of the Secret History with Brill Publishers; it was selected by Choice as Outstanding Academic Title (2005) and is now in its second edition. In 2007 he donated his personal library of around 6000 volumes to the Scheut Memorial Library.

Late in his life, de Rachewiltz was an emeritus Fellow in the Pacific and Asian History Division of the Australian National University. His research interests included the political and cultural history of China and Mongolia in the thirteenth and fourteenth centuries, East-West political and cultural contacts, and Sino-Mongolian philology generally.

Igor de Rachewiltz died on July 30, 2016. He was 87.