State-owned investors (SOIs), including sovereign wealth funds and public pension funds, have $27 trillion in assets under management in 2020, making these funds the third largest group of asset owners globally. SOIs have become the largest and are among the most important private equity investors, and they are key investors in other alternative asset investments such as real estate, infrastructure, and hedge funds. SOIs are also leaders in promoting environmental, social, and governance policies and corporate social responsibility policies in investee companies. We document the rise of SOIs, assess their current investment policies, and describe how their state ownership both constrains and enhances their investment opportunity sets. We survey the most impactful recent academic research on sovereign wealth funds, public pension funds, and their closest financial analogs, private pension funds. We also introduce a new Governance-Sustainability-Resilience Scoreboard for SOIs and survey research examining their role in promoting good corporate governance. Expected final online publication date for the Annual Review of Financial Economics, Volume 13 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.