Plagiaulacidae is a family of fossil mammals within the order Multituberculata. Remains are known from the Upper Jurassic of North America through the Lower Cretaceous of Europe. These small plant-eaters lived during the Mesozoic era, also known as the "age of the dinosaurs." They were among the more derived representatives of the informal suborder of "Plagiaulacida". The taxon Plagiaulacidae was named by Gill T.N. in 1872. It is also known as Bolodontidae, a name developed by Osborn H.F. in 1887.