Chlortoluron, chlorotoluron and CTU are the common names[3] for an organic compound of the phenylurea class of herbicides used to control broadleaf and annual grass weeds in cereal crops.

In 1952, chemists at E. I. du Pont de Nemours and Company patented a series of aryl urea derivatives as herbicides.

[7] As described in the du Pont patent, the starting material is a substituted aryl amine, an aniline, which is treated with phosgene to form its isocyanate derivative.

[12] It can be used to control broadleaf weeds and grasses including Alopecurus myosuroides, Anthemis arvensis, Atriplex prostrata, Calendula spp., Convolvulaceae spp., Galeopsis spp., Lamium spp., Papaver rhoeas, Paspalum distichum, Poa annua, Solanaceae spp., Stellaria media and Veronica spp.

[10][12] Chlorotoluron was banned in the UK in 2010, but in 2014 was reapproved after new formulations came with lower application rates, 250 g/Ha down from (up to) 3500 g/Ha, though farmers must spray it earlier in weeds' growth cycles.