Social and economic inequalities begin early. Presented in this paper is evidence that Early Childhood Development (ECD) can lead to gender equality and empowerment, better health and education outcomes, improved skills, abilities and productivity, narrow the income, ethnic, and geographic inequality gaps, provide timely intervention for persons with disabilities, and is a cost effective strategy for eliminating disadvantage. Inequity and inequalities are framed with respect to opportunities and outcome across dimensions of gender, income, health, education, ethnicity, language, disability, and geographic residence. ECD, a multifaceted construct, includes the child and the context. Promotive and positive relationships between these two facets can lead to achieving full human developmental potential. Many inequities in this foundational period are accentuated over the lifecycle, and persist throughout adulthood, with serious human, social and economic consequences. ECD evidence demonstrates that this foundational period is a window of opportunity for resolving early inequities, achieving inclusive social and economic development, peace and sustainability. Given that business as usual is no longer an option and transformative and holistic solutions are required to address the post‐2015 development challenges, this paper is a call to the development community to pay attention to the compelling, effective and relevant evidence based solutions that emanate from ECD.