Motsepe founded ARM's forerunner ARMgold in 1997 after starting out in contract mining, and built African Rainbow Minerals through mergers with Avmin and Harmony. A lawyer by training, he served as ARM's executive chairman until 16 February 2026, when he became non-executive chairman to comply with new JSE listings requirements; ARM appointed Jacques van der Bijl as its first chief operating officer at the same time.
