Over the past 25 years, tremendous progress has been made in increasing the evidence on child marriage and putting it to good use to reduce the prevalence of child marriage and provide support to married girls. However, there is still much to be done to achieve the Sustainable Development Goal target 5.3 of ending child marriage by 2030, and to meet the needs of the 12 million girls who are still married before age 18 each year. To guide and stimulate future efforts, the UNDP-UNFPA-UNICEF-WHO-World Bank Special Programme of Research, Development and Research Training in Human Reproduction, the World Health Organization, the UNICEF-UNFPA Global Programme to End Child Marriage, and Girls Not Brides: The Global Partnership to End Child Marriage convened an expert group meeting in 2019 to: (1) review the progress made in building the evidence base on child marriage since the publication of research priorities in this area in 2015, (2) identify an updated set of research priorities for the next ten years, and (3) discuss how best to support research coordination, translation, and uptake. This article provides a summary of the progress made in this area since 2015 and lists an updated set of research gaps and their rationale in four key areas: (1) prevalence, trends, determinants, and correlates of child marriage; (2) consequences of child marriage; (3) intervention effectiveness studies to prevent child marriage and support married girls; and (4) implementation research studies to prevent child marriage and support married girls. It also highlights a number of calls-to-action around research coordination and knowledge translation to support the emerging and evolving needs of the field.