This International Standard outlines lessons learned principles and guidelines that are applicable in all space project activities (management, technical, quality, cost and schedule). The application of this International Standard is intended to be included in the supplier quality management system, but can be tailored in individual contracts as agreed by the customer and supplier, depending on — the content of each project (size, technological level and novelty, particular organization, participants, etc.), and — the interest and usefulness of the related information. The lessons learned information can result from any situations which might be encountered in similar contexts for future projects, i.e. — undesirable experiences that need to be avoided; — strategies, rules, principles of design, validation, tests and operations that proved to be successful or necessary. This International Standard neither endorses nor recommends the transmission of company proprietary information to external entities as part of a lessons learned process. Implementing a formal lessons learned process as outlined in this International Standard makes it possible to capture and benefit from this information. The lessons learned activity is an important contribution to the processing of the preventive and corrective actions specified in ISO 9001 and ISO 17666. This International Standard also provides lessons learned processes and suggested lessons learned forms.