Hartman, who was previously managing director of the InterContinental Hotels Group (IHG), will assume his position after the company's annual general meeting on 7 May.
The previous chief executive, Peter Papadimitropoulos, left his position after less than six months, citing a "difference in management priorities".
Prior to joining IHG in 1998, Hartman was president of ITT Sheraton North America.
Chairman of Millennium & Copthorne, Mr Kwek Leng Beng, said: "We are fortunate to have secured such an experienced and senior individual as Richard and we look forward to benefiting from his strong operational skills as we continue to develop as a world class hotel group."
Acting chief executive Wong Hong Ren will revert to executive director once Hartman has taken up his role.
By Chris Druce
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