The U.S. Nuclear Regulatory Commission (NRC) is issuing Revision 1 to Regulatory Guide (RG) 5.71, "Cyber Security Programs for Nuclear Power Reactors." Revision 1 incorporates references to industry guidance on identifying and protecting critical digital assets for safety-related, important to safety, balance of plant, and emergency preparedness equipment. It also clarifies guidance on defense-in-depth for cyber security and includes updated text based on the latest National Institute of Standards and Technology (NIST) and International Atomic Energy Agency (IAEA) cyber security guidance. Specifically, this revision clarifies issues identified from cyber security inspections, insights gained through the Security Frequently Asked Questions (SFAQ) process, documented cyber security attacks, new technologies, and new regulations. This revision also considers the changes in the most recent revision to the NIST Special Publications (SP) 800-53, upon which Revision 0 of Regulatory Guide (RG) 5.71, "Cyber Security Programs for Nuclear Facilities" was based.