The Shadow is a Pureblood Heartless introduced in Kingdom Hearts. Although the Shadow is one of the weaker, more common types of Heartless, it is still a threat to those without the Keyblade.
A normal Shadow has a vaguely humanoid body structure. It has a round, spherical head with circular, glowing yellow eyes. It also has two long, twisted antennae sprouting out of the top of its head. Each of its hands has three clawed fingers, and its feet are large and lack any discernible digits. With the exception of its eyes, this Heartless's body is completely black (with the exception of the Shadows summoned by the Dark Follower, which are dark purple).
The Shadow's name is a reference to a shadow, highlighting its status as the most basic type of Heartless. The name could also be a reference to the Shadow's ability to flatten itself into a silhouette on the ground, and become a literal shadow.