Minister of Environmental Affairs Edna Molewa has died.
She was 61 years old.
She died in a Pretoria hospital "after a period of illness".
President Cyril Ramaphosa said in a statement: "I offer my deepest condolences to the family of Minister Edna Molewa as well as to her colleagues in Cabinet and across all spheres of government who have had the privilege to work alongside an extraordinary leader of our people.
"This is a devastating loss to our nation and to the global community who owe a great debt of gratitude to the late Minister Molewa for her championship nationally and globally for the environmental integrity of a sustainable planet Earth that can be shared and enjoyed by all nations and all people, rich and poor.
"Minister Molewa has distinguished herself in many capacities and causes from her contribution to our liberation to fighting for equality of women in our society. We shall miss her greatly," Ramaphosa said.
ANC spokesperson Pule Mabe said Molewa's death has left the party and country "poorer given her role in advancing the country's transformation agenda".
"She has been and will always remain a symbol of rare social and political activist who rose in the ranks of the democratic since her involvement in the trade unions before joining the North West provincial government as MEC in various departments before being a premier of the province," he said in a statement.
"Her role was noticeable and she was affirmed as a leader of the ANC NEC, NWC and a Cabinet minister in various departments. Our history as a country will not be complete without acknowledging the pivotal role that individuals like her played in enhancing the impact of the collective effort to make South Africa a better place."
Before being appointed to her current post in 2010, Molewa was the minister of social development and the first female premier of the North West.
A member of the ANC's national executive committee, Molewa became involved in the struggle in the 1970s and previously served as the deputy president of the South African Commercial, Catering and Allied Workers' Union (SACCAWU).
Ramaphosa has declared a period of mourning with immediate effect and ordered that the national flag be flown at halfmast at all flag stations countrywide and at South African diplomatic missions abroad.
Details of commemorative events and funeral arrangements would be communicated in due course, the Presidency said.
Ramaphosa, who is due to travel to New York later today for his inaugural participation as head of state and government in the United Nations National Assembly, is due to visit the Molewa family in the course of the day.
***This article has been edited since its first publication.***