Anthony Costello (born 20 February 1953) is a British paediatrician. Until 2015 Costello was Professor of International Child Health and Director of the Institute for Global Health at the University College London. Costello is most notable for his work on improving survival among mothers and their newborn infants in poor populations of developing countries. From 2015 to 2018 he was director of maternal, child and adolescent health at the World Health Organization in Geneva.

Costello was born in Beckenham, and graduated from school at St Joseph's Academy, Blackheath. Costello attended St Catharine's College, Cambridge, where he was awarded a degree in Experimental Psychology and qualified as a doctor in Medical Sciences after clinical training at the Middlesex Hospital in London. He then trained in Paediatrics and Neonatology at University College London. His aunt was the atheist activist Barbara Smoker.

After living in Baglung district in western Nepal from 1984 to 1986, two days' walk from a road, he became interested in challenges to mother and child health in poor, remote populations. His areas of scientific expertise include the evaluation of cost-effective interventions to reduce maternal and newborn deaths, women's groups, strategies to tackle malnutrition, international aid and the health effects of climate change. In 1999 he published a pioneering book on how to improve newborn infant health in developing countries.

With a Nepali organisation (MIRA), that he helped to establish, a large community trial of participatory learning and action using women's groups in the remote mountains of Makwanpur District, Nepal was published in The Lancet in 2004. He went on to establish partnerships and further studies with local organisations in East India, Mumbai, Bangladesh and Malawi. Seven cluster randomised controlled trials of women's groups in Nepal, India, Bangladesh and Malawi, led to a meta-analysis published in the Lancet in May 2013.

Results showed that in populations where more than 30% of pregnant women joined the women's group programme, maternal death and newborn deaths were cut by one third. The intervention has now been recommended by the World Health Organization (WHO) for scale-up in poor, rural populations.

Costello has led teams involved in more than a dozen cluster randomized controlled trials to show the power of community mobilization to affect health outcomes such as maternal and newborn deaths, child nutrition and diabetes. In November 2018 he published the book The Social Edge. The Power of Sympathy Groups for our Health, Wealth and Sustainable Future. The book explains why a new science of cooperation is needed and suggests twenty two social experiments which use sympathy groups for resolving 21st century problems.^{[citation needed]}

Costello chaired the 2009 Lancet Commission on Managing the Health Effects of Climate Change, and was co-chair of a new Lancet Commission which links the UK, China, Norway and Sweden on emergency actions to tackle the climate health crisis, published in June 2015. In 2015 he led the development of the Lancet Countdown: Tracking Progress on Health and Climate Change. These annual reports, developed by a network of 38 universities and research institutions, produces an annual Lancet report on the health impacts, adaptation progress, renewable energy, economics and public engagement related to climate change.

At WHO he helped to develop the Global Strategy for Women's, Children's and Adolescents' Health (2016‒2030) with its three objectives of surviving, thriving and transforming – to end preventable mortality, to promote health and well-being, and to expand enabling environments. Its guiding principles include equity, universality, human rights, development effectiveness and sustainability.