This chapter defines insider trading (i.e., the use of material nonpublic information for trading) and market manipulation (i.e., the artificial distortion of prices/volume). In addition, the chapter explains how insider trading and market manipulation corrode fairness, transparency, and trust. The chapter surveys core legal frameworks, including the Exchange Act rules, the Insider Trading Sanctions Act, the Dodd-Frank Act, and the EU’s MAR, and the roles of the SEC, FINRA, CFTC, and cross-border cooperation (IOSCO) in curbing market abuses. Through case studies, the discussion illustrates spoofing, wash trading, pump-and-dump schemes, and social-media amplify herding behavior and promote fraud. The chapter describes behavioral factors associated with unethical market behavior. The chapter also presents techniques that can be used to reduce insider trading and market manipulation, including pre-clearance, restricted lists, real-time surveillance and analytics, just-in-time ethics prompts, strong documentation, training, and confidential whistleblower channels. Emerging challenges are also presented, including DeFi anonymity laundering, alternative-data pathways to material nonpublic information (MNPI), bot-driven disinformation, adversarial AI, geopolitical influence operations, and regulatory arbitrage.