"Ms Byanyima brings a wealth of experience and commitment in harnessing the power of governments, multilateral agencies, the private sector and civil society to end the Aids epidemic around the world," UNAids said in a statement.

Her appointment followed "an open and wide-ranging search", UN chief Antonio Guterres said.

A former MP and engineer by training, Ms Byanyima succeeds Michel Sidibé, who has been appointed Mali's health minister.

“I am honoured to be joining UNAids as the executive director at such a critical time in the response to HIV,” Ms Byanyima said in a statement.

“The end of Aids as a public health threat by 2030 is a goal that is within the world’s reach, but I do not underestimate the scale of the challenge ahead,”she added.

Ms Byanyima, 60, tweeted that she embraces the role with "humility, passion and faith":

Winnie Byanyima?@Winnie_Byanyima

 An honour 2 be asked 2 lead the UN & global  HIV response! I embrace the role with humility, passion & faith that we can end this pandemic by 2030. I look fwd to joining  @UNAIDS team & working closely with co-sponsors & partners 2  remove barriers to prevention, treatment & care https://twitter.com/unaids/status/1161738408135483393 …

UNAIDS?@UNAIDS

UNAIDS warmly welcomes the appointment of @Winnie_Byanyima as its new Executive Director: http://bit.ly/2TDsoJS

Ms Byanyima is married to Ugandan opposition leader Kizza Besigye, with whom she has a son.

She served for seven years as director of gender and development at the United Nations Development Programme (UNDP) before she joined Oxfam in 2013.

She has also worked for the African Union Commission on a women's rights project to help reduce the disproportionate effect of HIV on the lives of women on the continent.