Community engagement, which is also called public participation, is a key component of social impact assessment (SIA). However, although overlapping, the professional fields of practice of public participation and SIA are separate discourses and communities of practice. Although they share many goals and principles, and draw on similar techniques, they are pursued for different reasons. Put bluntly, SIA and public participation, though similar and related, are not the same (Vanclay et al., 2015). While SIA requires community engagement, public participation has a wide range of applications across many sectors. A lack of appreciation of this difference has led to the fields of SIA and public participation being conflated by various stakeholders.SIA is the process of analysing and managing the social consequences arising from planned interventions (Vanclay, 2003;Esteves et al., 2012;Vanclay et al., 2015). While the terms 'community engagement' and 'public participation' are somewhat interchangeable (including in this chapter), for various reasons some practitioners have a preference for one or the other term. SIA practitioners generally prefer use of 'community engagement', whereas public participation professionals tend to use 'public participation'. In an environmental impact assessment (EIA) context, 'public participation' is generally regarded as being the act of involving the individuals and groups who are positively or negatively affected by a proposed intervention that is subject to a formal decision-making process (André et al., 2006). Community engagement is regarded as being broader and refers to any attempt by a project or organisation to interact (engage) with its host communities and broader publics, irrespective of any formal requirement (OECD, 2017(OECD, , 2022. It is important to realise that, while participation/engagement around projects may not be a formal requirement of national legislation in all countries, it is nevertheless a strong expectation or requirement of international standards, and is a requirement of all international financial institutions (Vanclay & Hanna, 2019). Also important to note is that what is usually intended by participation or engagement is more than 'consultation', which is simply the collection of the views of people about something, such as a proposed project or activity.This chapter discusses community engagement and public participation in different settings, untangles the unhelpful conflation with SIA, and clarifies the distinctions, synergies, and characteristics of good practice. It draws on the key international frameworks that guide public participation and SIA practice, specifically those of the International Association for Public Participation (IAP2), notably the IAP2 Spectrum of Public Participation (IAP2, 2018), and those of the International Association for Impact Assessment (IAIA) that relate to public participation (