Glyphosate (N-(phosphonomethyl) glycine, C3H8NO5P) was used, before the advent of crops resistant to it, as a non-selective herbicide, especially perennial weeds. It kills plants by inhibiting their ability to make aromatic amino acids. It was first sold by Monsanto under the tradename Roundup. It is no longer under patent so it is sold under numerous other names.
Glyphosate is one of a number of herbicides used by the United States government to spray Colombian coca fields through Plan Colombia. Its health effects, effects on legal crops, and effectiveness in fighting the war on drugs have been disputed heavily.