The formation of human capital--the knowledge, skills, and health that people accumulate over their lifetimes--is critical for the six Gulf Cooperation Council (GCC) countries. Human capital contributes not only to human development and employment but also to the long-term sustainability of a diversified economic growth model that is knowledge based and private sector driven. This approach is critical, given that income from oil and gas will eventually decline and that the nature of work is evolving in response to rapid technological changes, in turn demanding new skill sets. The GCC governments have demonstrated their strong political will for this shift: four of them are among the first countries to join the World Bank's Human Capital Project-a global effort to improve investments in people as measured by the Human Capital Index. The GCC countries face four main challenges:* Low levels of basic proficiency among schoolchildren* A mismatch between education and the labor market* A relatively high rate of adult mortality and morbidity* A unique labor market , in which wages in the public sector are more generous than in the private sector and government employment of nationals is virtually guaranteed. To address these challenges, this report outlines four strategies in a "whole-of-government" approach:* Investing in high-quality early childhood development* Preparing healthier, better educated, and skilled youth for the future* Enabling greater adult labor force participation* Creating an enabling environment for human capital formation. These strategies are based on best practices in other countries and feature some of the GCC countries' plans, including their national "Visions," to take their economies and societies further into the twenty-first century. With the COVID-19 pandemic, the GCC countries face additional challenges that may worsen some pre-existing vulnerabilities and erode human capital. In response, the GCC governments have taken multiple measures to protect their populations' health and their economies. Any country's decision to reopen its economy needs to closely consider public health consequences to avoid a resurgence of infections and any further erosion of its human capital. The COVID-19 crisis underscores that the need to accelerate and improve investment in human capital has never been greater. Once the GCC countries return to a "new normal," they will be in a position to achieve diversified and sustainable growth by adopting, and then tailoring, the strategies presented in this report.