Present trends suggest that many of the poorest countries in the world, including many in sub-Saharan Africa, will not meet the health-related Millennium Development Goals (MDGs), especially MDG 4 (reducing under-five mortality) and MDG 5 (reducing maternal mortality). Even in those countries that are on track to meet health MDGs, striking inequities exist among countries and among socioeconomic groups within them, despite effective and cost-effective interventions being available to improve population health, including that of vulnerable groups. Such interventions are delivered through health systems, which consist of “all organisations, people and actions whose primary intent is to promote, restore or maintain health”, but, in many settings, interactions between weakened health systems and the sometimes conflicting demands of single-disease intervention programmes are hindering the uptake and implementation of life-saving interventions. A growing number of governments, international institutions, and funding agencies have therefore recognised the urgent need to coordinate and harmonise investments in health systems strengthening in low- and middle-income countries (LMICs) to provide universal social protection and effective coverage of essential health interventions.