OM Holdings chief executive Peter Toth has announced his resignation from the role in order to take up a senior posting with an unnamed multinational resources group.
Mr Toth has led the manganese miner since 2008 and will depart at the beginning of April.
OM chairman Low Ngee Tong will assume the chief executive role until a permanent replacement is appointed,
Mr Toth said the company's Sarawak ferro-alloy smelting project in Malaysia and investment in the Tshipi manganese project in South Africa would prove to be a "game-changer" for the company and the industry at large.
OM shares closed the day's trade 1.3 per cent higher at 40 cents.