Despite increasing evidence about the value and importance of breastfeeding, less than half of the world's infants and young children (aged 0–36 months) are breastfed as recommended. This Series paper examines the social, political, and economic reasons for this problem. First, this paper highlights the power of the commercial milk formula (CMF) industry to commodify the feeding of infants and young children; influence policy at both national and international levels in ways that grow and sustain CMF markets; and externalise the social, environmental, and economic costs of CMF. Second, this paper examines how breastfeeding is undermined by economic policies and systems that ignore the value of care work by women, including breastfeeding, and by the inadequacy of maternity rights protection across the world, especially for poorer women. Third, this paper presents three reasons why health systems often do not provide adequate breastfeeding protection, promotion, and support. These reasons are the gendered and biomedical power systems that deny women-centred and culturally appropriate care; the economic and ideological factors that accept, and even encourage, commercial influence and conflicts of interest; and the fiscal and economic policies that leave governments with insufficient funds to adequately protect, promote, and support breastfeeding. We outline six sets of wide-ranging social, political, and economic reforms required to overcome these deeply embedded commercial and structural barriers to breastfeeding.