Steele has been serving as interim chief executive of Save the Children UK since February, when she stood in between the departure of Justin Forsyth and the arrival of the charity’s new head Kevin Watkins.
She previously spent 12 years as the charity’s executive director for marketing, fundraising and communications.
She will begin her new role on 1 January, three months after Nussbaum departs to become chief executive at peace and human rights organisation The Elders. Glyn Davies, executive director of global programmes at WWF-UK will act as interim chief executive until Steele joins.
In a statement announcing her appointment, WWF-UK said Steele would take over leadership of the charity in a key moment in its history. "Tanya will be a leading figure, both in the UK and in the global WWF Network, working for deeper and quicker measures to protect the natural world," it said.
Sir Andrew Cahn, chair of trustees at WWF-UK, also said he was delighted with the appointment. "She has the enthusiasm, the energy and the commitment, as well as the very strong leadership and managerial skills, which we need for the next stage in our journey," he said.
Before joining Save the Children, Tanya spent over a decade working in product development, marketing and communications in the technology sector, holding senior roles at Siemens and BT.