Population and development are inextricably interrelated. Population size and structure are crucial factors affecting opportunities, pressures, and constraints of society. The high fertility and rapid population growth in low-resource countries have hampered socio-economic development. However, as fertility began to fall rapidly since the middle of the 20th century, many post-demographic-transition countries are undergoing rapid population ageing and encountering labour shortages Sabah is the second-most populous state in Malaysia, with about 4 million population in 2020. It has registered the second-highest population growth rate over the past four decades, brought about by the influx of migrant workers due to the severe labour shortage. The number of non-citizens grew from 420 thousand in 1990 to 1.094 million in 2020. Non-citizens made up close to 30% of the state population during 2013 – 2018, up from around 26% in 2009 – 2010. However, the negative growth of the non-citizens in Sabah during 2018 – 2020 has resulted in zero growth of the state population. This book is a sequel to the series on “Revisiting Population- Development Nexus: The Past in Its Future, 2016”, and “Demographic Transition and Socio-economic Development in Malaysia, 2020”by the Universiti Malaysia Press. Given Sabah’s unique socio-demographic situation, this book will provide a comprehensive analysis of the demographic situation, emphasizing the young generation and the changing roles and status of women in Sabah. The book consists of 14 chapters, covering population situation analysis at the state and district levels; functional population projection; gender differentials in education, employment, and income; internal and international migration; marriage; fertility and fertility preferences; family planning; family and gender roles; youth in development; adolescent sexual and reproductive health; women and youth in the hotel industry; and growth of the non-citizen population. Each chapter examines gender differentials and provides a comparative analysis with Sarawak and Peninsular Malaysia. The book will serve as a useful reference for planners and administrators from the public and private sectors, researchers, and students.