M. Popillius M.f. Laenas was a consul of the Roman Republic in the year (according to Varro) 359 BC. Whle consul, he defeated a Gallic army.

Near the end of his consulship with Cn. Manlius L.f. Capitolinus Imperiosus, the Tarquinians invaded the Roman territories on the Etruscan border (Livy VII, 12). Polybius (II, 18.1 - 20.7) is correct in stating that this Gallic war took place 30 years after the occupation of Rome by the Gauls (in 386/5 BC). Dio Cassius apparently identifies this war with the one in Furius Camillus' 5th dictatorship when the election of the consuls was resumed. Those events took place in 364 BC, about a decade earlier, as Livy VI, 42 tells.