This document specifies the organizational context and underlying concepts for undertaking project, programme and portfolio management. It also provides guidance for organizations to adopt or improve project, programme and portfolio management using the standards prepared by ISO/TC 258. This document is applicable to most organizations, including public and private organizations and it is not dependent on the size and type of the organization. It is also applicable to any project, programme and portfolio, regardless of complexity, size or duration. Further guidance on project, programme and portfolio management, and the governance thereof, is given in ISO 21502, ISO 21503, ISO 21504 and ISO 21505.