Deltatheridium (meaning triangle beast or delta beast) is an extinct species of metatherian. It lived in what is now Mongolia during the Upper Cretaceous. It was a basal metatherian, which places it near start of the linage that led to the marsupials, such the kangaroo, koala, and opossum.
It had a length of 15 cm (5.9 in). Apart from preying on insects, its diet was also composed of small reptiles and what it could scavenge from carrion using its sharp canine teeth.