Southeast Asia Primary Learning Metrics (SEA-PLM) is a new regional large-scale student learning assessment programme, designed by and for countries in Southeast Asia. The programme aims to generate reliable data and evidence for monitoring learning outcomes across and within countries, and to understand what factors facilitate or hinder effective learning of children along their school journey. By doing so, each participating country can develop and implement policies and programmes to improve students’ learning outcomes. SEA-PLM 2019 is the first round of this regional assessment. Six countries from the region participated in SEA-PLM 2019: Cambodia, Lao PDR, Malaysia, Myanmar, Philippines and Viet Nam. This first round focused on Grade 5 students, and on 3 learning domains: reading, writing and mathematics. A global citizenship questionnaire module was also developed as an experimental exercise in comparative large-scale assessment at primary education level. In addition, SEA-PLM 2019 used a series of background questionnaires to collect extensive information about children, classrooms, schools, teachers, head teachers, parents and communities.