Fifth-generation (5G) networks are being deployed in the United States and globally and one day will replace many older third-and fourth-generation cellular networks. 5G will provide much higher data rates and lower message latency than any previous generation of cellular network technology. With its advanced capabilities, 5G could enable important new applications. A few possible examples are autonomous connected cars, telemedicine, and augmented reality games and environments. However, security concerns have been raised about 5G networks built using Chinese equipment and 5G phones made by Chinese companies. The United States relies on foreign suppliers for 5G infrastructure and key microchips that go into every 5G phone.This report examines 5G security issues, the 5G supply chain, and the competitive landscape in 5G equipment and mobile device markets. It describes where U.S. or Chinese companies have technology or market advantages in the emerging 5G security competition between the United States and China. The report provides recommendations for securing U.S. 5G networks and mobile devices and those used by U.S. allies and foreign partner nations.