Rigid ryegrass (Lolium rigidum Gaudin) is the most problematic weed in Australia, with evolved resistance to multiple herbicide sites of action. Selection pressure by cinmethylin (Group 30, a fatty acid thioesterase inhibitor) has been limited because few populations have been exposed to the herbicide since its introduction in 2019. In this study, we examined the sensitivity of L. rigidum populations to this new herbicide.