Viljoen will take up the role on April 16 following Chris Griffith's departure after seven years in charge. Griffith is tipped as a possible successor to Anglo's current CEO Mark Cutifani.
Viljoen has been head of processing at Anglo since 2014, before which she was executive vice president of processing at Lonmin. She began her career as an engineer at Iscor and has also held leadership positions at AngloGold and was general manager of BHP's Klipspruit Colliery before joining Lonmin in 2008.
"Natascha is a seasoned senior executive, bringing 28 years of operational experience from across our mining industry, spanning many different countries, metals and minerals including, of course, the PGMs," said Norman Mbazima, chairman of Anglo American Platinum.