The number of sustainability standards and certifications applied in agricultural supply chains has grown considerably in the past decade. A recent United Nations report suggests that there are in the region of 450 voluntary sustainability standards (VSSs), most covering agricultural commodities (UNFSS, 2022). This chapter provides an overview of the range of sustainability standards that have emerged, who has developed them, their content and rationale. Concerns have been raised as to whether sustainability standards create barriers to inclusion and in fact limit the benefits of incorporation in so-called modern markets for smallholders. Ultimately, standards need to be considered both in terms of the standards system of which they are only one part and the wider social and institutional context in the country of production. Too often standards are regarded as ‘off the shelf’ supply chain management tools that ignore the interface with local context and the market power of those who choose to use them.