Both acute malnutrition and nutrition (breastfeeding) in infants under 6 months of age (infants <6 months) are important global health issues and have received much international attention over the years. However, it is only recently that the two in combination—the management of acute malnutrition in infants <6 months (MAMI)—have been examined [1]. This chapter outlines the background epidemiology, why acute malnutrition in this age group matters, key challenges around infant <6 months malnutrition, current assessment and treatment strategies, and, finally, directions for the future. Readers should look to other chapters of this book for added detail, as 208MAMI has numerous links and synergies with other areas of malnutrition, with many opportunities to benefit both short- and long-term health.