Pirimiphos-methyl, marketed as Actellic[1][2][3][4] and Sybol, is a phosphorothioate used as an insecticide.

It was originally developed by Imperial Chemical Industries Ltd., now Syngenta, at their Jealott's Hill site and first marketed in 1977, ten years after its discovery.

These insects are implicated in the transmission of Chagas disease in the Americas.

[7] Pirimiphos-methyl can be applied as an interior surface paint additive, in order to achieve a residual pesticide effect.

Pirimiphos methyl is manufactured in a two-step process in which N,N-diethylguanidine is reacted with ethyl acetoacetate to form a pyrimidine ring and its hydroxy group is combined with dimethyl chlorothiophosphate to form the insecticide.