Dr Osuji joins NHS North East London (NEL) from the Royal Free London NHS Foundation Trust where she serves as chief executive for North Middlesex University Hospital and community services.
Prior to this, she was deputy chief executive at Croydon Health Services NHS Trust.
She is an experienced haematology consultant and continues to practise.
Dame Marie Gabriel, chair of NHS North East London, said: ‘We will benefit from Nnenna's insight and strategic approach, her overriding commitment to people and to tackling inequalities and from her vision, energy and focus on outcomes. Importantly, she also brings compassion and openness at a time of great change for our staff, the NHS and the wider public sector.
‘Nnenna is ideally placed to lead NEL into the future as we focus on our role as strategic commissioners in one of the most diverse and vibrant areas of the country. This includes building on our work to deliver the ambitions of the national 10-Year Health Plan, and our drive to work meaningfully with our communities and partners to improve population health and service delivery.'
Dr Osuji replaces Zina Etheridge, the ICB's founding chief executive, who served for four years.
Dr Osuji said: ‘My priority is ensuring our staff are supported through a period of change and able to focus on our role as strategic commissioners, so we can continue to play a key role in providing local people with safe, quality and compassionate care.'
Dame Caroline Clarke, regional director for the NHS in London, added: 'Nnenna is an experienced and strategic leader, with a strong track record in delivering services across London. Her commitment to people is evident in her work as co-chair of the London People Board and the London steering group on equality, diversity and inclusion.
'I look forward to working with Nnenna in this new capacity, with our ICBs playing a key role in London's delivery of the 10-Year Health Plan.'
