This introduction reviews recent research on hedge funds. The Handbook of Hedge Funds comprises 21 chapters from authors around the world. The chapters describe hedge fund industry governance, flows, limited partnership contracts, compensation, fund strategies, performance, activism, effects on investee firms, misconduct, misreporting, fraud, and financial regulation. Further, the chapters highlight differences with other types of intermediaries, such as private equity funds and mutual funds. The chapters feature both US and international analyses. This introductory chapter summarizes papers that appear in the handbook, provide a theoretical framework for research on hedge funds, and highlight research trends on topic.