Sriskandarajah is currently Secretary General and CEO of CIVICUS, the Johannesburg-based global alliance of civil society organisations and activists with members in more than 180 countries. He joined CIVICUS in 2013 and was previously Director General of the Royal Commonwealth Society (2009-13). Between 2011-12 he was seconded to be Interim Director of the Commonwealth Foundation.
Sriskandarajah said: "I am excited by the opportunity of leading Oxfam at this crucial point in its history. It is an organisation which has spent more than three-quarters of a century doing amazing things to help people escape poverty and the hunger, disease and discrimination that come with it.
"At a time when hunger is once again on the increase, almost 70 million people have been forced to flee their homes by conflict and persecution and many countries are increasingly looking inwards, the UK and the world need a strong Oxfam more than ever."
Born in Sri Lanka, Sriskandarajah - who is known as Danny - grew up in Australia and Papua New Guinea, before moving to the UK in 1998. He has been a British citizen for almost 10 years.
Caroline Thomson, Oxfam Chair of Trustees, said: "From a very strong short list Danny was clearly the right person to lead Oxfam on the path of change and renewal. He has a deep understanding of the challenges facing the sector as a whole, including on gender justice. He is a brilliant strategic thinker with a record of delivery.
"One of the next generation of leaders, he inspires those who work with him and has a global reputation for original thinking. Above all, we felt he would ask the difficult questions and work well with colleagues across the Oxfam confederation to come up with the answers."
Oxfam GB's current Chief Executive Mark Goldring announced in May that he would step down by the end of the year because he believed fresh vision and energy were required to shape Oxfam's future as it implements the lessons learned from its past safeguarding mistakes.
Sriskandarajah is expected to take up his post around the end of 2018.