"The resignations follow the board's evaluation of its structure, composition and succession plan conducted on an annual basis," the company said yesterday.
It said Ken Dicks and Max Sisulu had resigned as independent non-executive directors (NEDs) and executive director Frank Abbott had retired, effective September 30.
"Max, Ken and Frank have made valuable contributions to the success of Harmony," chairman Dr Patrice Motsepe said.
"The board and I wish to thank each of them for their guidance and advice as board members over the years."
The board now comprises Motsepe, deputy chairman Modise Motloba, CEO Peter Steenkamp, financial director Boipelo Lekubo, executive director Harry Mashego and lead independent NED Mavuso Msimang, and 9 NEDs, of whom four are women.
Harmony today takes over the world's deepest gold mine, Mponeng, as part of its acquisition of AngloGold Ashanti's remaining assets in South Africa in a transaction which closed yesterday.
Harmony shares (JSE: HAR) closed down 3.19% in Johannesburg to 8,914c, capitalising it at R53.2 billion (US$3.2 billion).