Self-regulation has been established as a key mechanism associated with a variety of outcomes, including school readiness (Blair & Razza, 2007; McClelland, Cameron, Connor, et al., 2007; Morrison, Ponitz, & McClelland, 2010), academic achievement (Cameron Ponitz, McClelland, Matthews, & Morrison, 2009; Duckworth, Tsukayama, & May, 2010; Li-Grining, Votruba-Drzal, Maldonado-Carren~o, & Haas, 2010; McClelland, Acock, & Morrison, 2006), and long-term health and educational outcomes (McClelland, Acock, Piccinin, Rhea, & Stallings, 2013; Moffitt et al., 2011). Researchers have described self-regulation from a diverse set of perspectives and experts agree that self-regulation has important implications for individual health and well-being starting early in life (Geldhof, Little, & Colombo, 2010; McClelland, Cameron Ponitz, Messersmith, & Tominey, 2010). In this chapter, we describe the development of self-regulation in young children. We begin by defining self-regulation and related constructs, and then discuss how self-regulation develops over time and how socio-demographic risk plays a role in this development. We then focus on the importance of self-regulation for school success and as a protective factor. Although we highlight children living in a North American context, we also connect findings and research to children in other countries. We discuss how to best measure these skills in young children and advances in interventions to promote self-regulation. Finally, we discuss implications for research and practice. [This chapter was published in: "The SAGE Handbook of Developmental Psychology and Early Childhood Education," edited by D. Whitebread, et al., SAGE Publications, Limited, 2019, pp. 471-486.]