Cloud computing technology and services provide the Department of Defense (DoD) with the opportunity to deploy an Enterprise Cloud Environment aligned with Federal Department-wide Information Technology (IT) strategies and efficiency initiatives, including federal data center consolidation. Cloud computing enables the Department to consolidate infrastructure, leverage commodity IT functions, and eliminate functional redundancies while improving continuity of operations. The overall success of these initiatives depends upon well executed security requirements, defined and understood by both DoD Components and industry. Consistent implementation and operation of these requirements assures mission execution, provides sensitive data protection, increases mission effectiveness, and ultimately results in the outcomes and operational efficiencies the DoD seeks. The 15 December 2014 DoD CIO memo regarding Updated Guidance on the Acquisition and Use of Commercial Cloud Computing Services defines DoD Component responsibilities when acquiring commercial cloud services. The memo allows components to responsibly acquire cloud services minimally in accordance with the security requirements outlined in Federal Risk and Authorization Management Program (FedRAMP) FedRAMP and this Security Requirement Guide (SRG). DISA previously published the concepts for operating in the commercial cloud under the Cloud Security Model. Version 1 defined the overall framework and provided initial guidance for public data. Version 2.1 added information for Controlled Unclassified Information. This document, the Cloud Computing Security Requirements Guide (SRG), documents cloud security requirements in a construct similar to other SRGs published by DISA for the DoD. This SRG incorporates, supersedes, and rescinds the previously published Cloud Security Model.