Our estimates indicate that about 30% of the seven million square kilometers that make up the Amazon basin comply with international criteria for wetland definition. Most countries sharing the Amazon basin have signed the Ramsar Convention on Wetlands of International Importance but still lack complete wetland inventories, classification systems, and management plans. Amazonian wetlands vary considerably with respect to hydrology, water and soil fertility, vegetation cover, diversity of plant and animal species, and primary and secondary productivity. They also play important roles in the hydrology and biogeochemical cycles of the basin. Here, we propose a classification system for large Amazonian wetland types based on climatic, hydrological, hydrochemical, and botanical parameters. The classification scheme divides natural wetlands into one group with rather stable water levels and another with oscillating water levels. These groups are subdivided into 14 major wetland types. The types are characterized and their distributions and extents are mapped.

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Vegetation on sandy soils, ranging from open grasslands and shrublands to closed‐canopy, thin‐trunked forests, can be found in patches throughout the Amazon. Despite variation in names, appearance, ecological correlates, and suggested origins, these ‘white‐sand ecosystems’ (WSE) share distinctive characteristics and biological communities. Here, in the first Amazon‐wide review of WSE, we review the variation in WSE and the factors underlying this variation. We present the most comprehensive Amazon‐wide map to date of WSE and calculate their total area. We find that WSE are still not completely mapped, and we use biological correlates as a proxy to indicate where white‐sand vegetation patches likely occur. Through our synthesis of the literature, we find that key factors, such as geologic origin, soil characteristics, hydrology, and fire regimes, vary widely and have differing impacts in different regions on vegetation structure and on floral, faunal, and fungal species composition. Although studies of WSE have increased dramatically in recent years, WSE in many parts of the Amazon remain understudied, and there is little synthesis of the interaction of factors across different areas. In response, we suggest priorities for future research. Finally, we find that WSE are inadequately protected and, where accessible, are regularly mined for sand, logged, or burned and cleared for agriculture. We argue that due to their island‐like distribution patterns and resultant complex metapopulation dynamics, their extremely slow recovery after disturbance, and their important contributions to basin‐wide diversity patterns and ecosystem services, WSE should be given special consideration in conservation efforts to ensure their persistence in Amazonia.