The present invention relates to thiadiazolyloxyphenylamidines of the general formula (I), to a process for the preparation thereof, to the use of the amidines according to the invention in combating undesirable microorganisms and to a composition for this purpose comprising the thiadiazolyloxyphenylamidines according to the invention. The invention furthermore relates to a method for combating undesirable microorganisms by application of the compounds according to the invention to the microorganisms and/or to the habitat thereof.