The Masked Shrew, Sorex cinereus, is a small shrew found in Alaska, Canada, the northern United States, and northeastern Siberia. This is the most widely distributed shrew in North America and it is also known as the Common Shrew there.

It is grey-brown in colour with light grey underparts. It has a long tail which is brown on top and pale underneath with a dark tip. Its body is about 9 cm in length including a 4 cm long tail. It weighs about 5 g.

These animals are found in humid areas and damp northern forests. Their range extends further south along the Rocky Mountains in the west and the Appalachians in the east. This species was introduced into Newfoundland in the late 1950s.

They eat insects, worms, snails, small mammals, salamanders and seeds. They have voracious appetites, even for a shrew, and can eat their own body weight in a day. Predators include larger shrews, hawks, owls, shrikes, snakes, herons, and foxes.

These animals are active day and night year-round. They dig tunnels but also use tunnels created by other small mammals. They mate between spring and fall. 3 to 6 young are born in a nest under a log or in a stump. In the north, females have only one litter per year. These animals usually live less than 18 months.

These animals are common and wide-spread but little-known.