Heavy metal contamination has caused serious impacts on the environment and risks towards human health, promoting intensive R&D efforts for the removal of heavy metals from their primary sources (industrial and agricultural wastewater). Among all developed techniques, the adsorption removal approach has attracted the most attention. This article reviews the recent developments in adsorbents for removing heavy metal ions from wastewater in the past decade (2011–2020). It starts with design principles, followed by the synthesis and performances of adsorbents for removing various heavy metals with 210 references. The developed adsorbents mainly include carbon materials (activated carbon, nanotubes, graphene, and biochar), polymers, metals and metal compounds (nanoparticles, MXenes, metal–organic frameworks, and magnetic materials), minerals (silica, zeolites, and clays), boron and carbon nitrides, industrial and agricultural wastes, and functionalized mesoporous materials. The challenges and prospects are also discussed.