As of April 2022, the United Nations Conference on Trade and Development (UNCTAD) tallied 3,218 international investment treaties, of which 2,558 are in force. Investors in extractive industries (the oil, gas, and mining sectors) have used investor-state dispute settlement (ISDS) mechanisms embedded in these treaties to challenge a wide range of host state actions and inactions that have allegedly negatively affected their investments. Those claims, and the threats thereof, restrict states’ ability to maximize the benefits, and their ability to limit environmental and social harms, resulting from the exploitation of natural resources. This briefing note provides an introduction to international investment law, to assist stakeholders in grasping its diverse and significant implications for the governance of investments in extractive industries.