Increasing global dependence on cyberspace, rapidly and continuously changing technology, sustained vulnerabilities, and advanced persistent threats are driving an increasing societal risk of attack in cyberspace. Assuring a broad range of infrastructure critical for a well-functioning society is essential in a broad range of areas including but not limited to communications, transportation, and commerce. Based on an engagement with government, industry, and academia, and building upon prior research in computer security principles, this chapter articulates a set of enduring cybersecurity principles that can serve as a focusing framework to improve trust and assurance of systems considering requirements, architecture and design, and operations and maintenance. This chapter first outlines the threat and its consequence, describes prior research in cybersecurity principles, and then outlines a set of succinct and actionable cybersecurity principles.