Amaranthus hybridus, commonly called green amaranth,<ref name=BSBI07>Template:Cite web</ref> slim amaranth,<ref>Template:PLANTS</ref> smooth amaranth, smooth pigweed, or red amaranth, is a species of annual flowering plant. It is a weedy species found now over much of North America and introduced into Europe and Eurasia.
Amaranthus hybridus was originally a pioneer plant in eastern North America. It has been reported to have been found in every state except Wyoming, Utah, and Alaska. It is also found in many provinces of Canada, and in parts of Mexico, the West Indies, Central America, and South America. It has been naturalized in many places of warmer climate. It grows in many different places, including disturbed habitats.
It is extremely variable, and many other Amaranthus species are believed to be natural hybridizations or derive from A. hybridus.
As a weed
Although easily controlled and not particularly competitive, it is recognized as a harmful weed of North American crops. The plant was used for food and medicine by several Native American groups and in traditional African medicine. Its is among the species consumed as Quelite quintonilli in Mexican food markets.