This chapter provides an overview of the rationale, principles, methods and approaches for human rights impact assessment (HRIA) in business and human rights (BHR) - spanning project, sector and governance levels. The chapter addresses the requirements for HRIA posed by key frameworks, such as the United Nations Guiding Principles on Business and Human Rights, and introduces the different approaches outlined in the Handbook: company-commissioned assessments; community-based assessments; collaborative approaches; sector-wide assessments; and HRIA of trade agreements. The original elements of HRIA are outlined, demonstrating the value added of this methodology, as well as emerging good practice criteria for the content and process of HRIA. Key challenges in current practice are flagged - such as effectiveness, participation, accountability and the role of local context. The chapter also touches on the role of different actors, frameworks and standards in HRIA as well as the role of impact assessment in the 2030 Agenda for Sustainable Development.