Amaranthus spp. are plants with proven allelopathic potential. The release of allelochemicals from Amaranthus spp. in the environment can influence seed germination, photosynthesis rate, reduce growth and, consequently, the productivity of various plant species. Among the species with allelopathic potential are Amaranthus blitoides, Amaranthus gracilis, Amaranthus hybridus, Amaranthus palmeri, Amaranthus retroflexus, Amaranthus spinosus and Amaranthus viridis, with A. retroflexus being the most studied species and A. spinosus being the species with the greatest allelopathic potential. Due to the large quantities of allelochemicals produced by Amaranthus spp. these plants stand out as future suppliers of chemical molecules for bioherbicides and semisynthetic herbicides.