Cynmethylin (or cinmethylin) is a preёmergent cineole herbicide used in Australia on wheat, and commonly for rice and cereal crops. It is the only Group T (Aus) (Group Q, global, Group 30, numeric) herbicide. It controls annual ryegrass and the unusual mode of action avoids resistance. It works by inhibiting fatty acid thioesterase, disrupting cell membranes. It was introduced in 1989. As of 2025, approval is pending in Europe.
Cynmethylin can provide 12 weeks' residual control.
It is sold under the tradenames "Luximax", "Cinch" and "Argold".