He will replace David Bull, who will retire in June – a month after Penrose joins Unicef.
Penrose, who has been at ACF since October 2013, has also worked as humanitarian director at Save the Children International, and has held positions at the Department for International Development and Oxfam and worked as a consultant to several UN agencies.
Bull was appointed executive director in 1999. During his time at Unicef, he led the introduction of the Rights Respecting Schools Award in the UK and was awarded a CBE in the 2015 Queen’s Birthday Honours for his humanitarian services.
Penrose said: "I’m thrilled to be joining Unicef UK and am honoured to be taking over from David Bull, whose work has had an enormous impact on some of the world’s most disadvantaged children. "At a time when so many children’s lives are being torn apart by war, poverty, disease and hunger, the work of Unicef has never been so important and I can’t wait to begin doing my part."
Bull said it has been a privilege to work at Unicef. "While I shall be sad to complete my time as Unicef UK’s executive director, I have the utmost confidence that Michael will do an incredible job driving forward the work of the organisation, helping children in danger around the world," he said.
Ilse Howling, chair of Unicef UK, said: "I’m delighted we are appointing a humanitarian leader who has such an outstanding track record of delivering growth in action, influence and income to protect the most disadvantaged. Mike brings a wealth of excellent experience and a passion for children’s rights that make him the perfect choice for the role.
She also paid tribute to Bull’s leadership, "which has transformed Unicef UK to become the country’s leading child rights charity".
She said: "His dedication and energy on behalf of the world’s most vulnerable children has been extraordinary."
Unicef UK declined to reveal details of Penrose's salary, but said they would be available in the trustees' report after the end of the next financial year. Bull was paid £116,932 in 2014, plus a £9,822 pension.
Unicef had an income of £93.7m in the year to 31 December 2014, against expenditure of £92.7m. It employs more than 250 people in the UK.