Mailleux will be based in Hong Kong and start his new role in November.
He will report to David Russell, head of markets for the Asia region, as well as Adam Herrmann, global head of prime finance.
In his new role, Mailleux will be responsible for prime services, equity finance, agency securities lending and delta one across the Asia Pacific region, as well as Japan.
Prior to Citi, Mailleux was head of prime trading at BNP Paribas.
The appointment of Mailleux follows Citi’s recruitment of Jason Massey as head of sales for Europe, the Middle East and Africa (EMEA) futures, clearing and collateral.