Monocular vision is vision in which each eye is used separately. By using the eyes in this way, as opposed by binocular vision, the field of view is increased (it says decreased in the later section please clarify), while depth perception is limited. The eyes are usually positioned on opposite sides of the animal's head giving it the ability to see two objects at once. The word monocular comes from the Greek root, mono for one, and the Latin root, oculus for eye.

Most birds and lizards (except chameleons) have monocular vision. Owls and other birds of prey are notable exceptions. Also many prey have monocular vision to see predators.

Monocular vision impairment refers to having no vision in one eye with adequate vision in the other.^{[dead link]}

Monopsia is a medical condition in humans who cannot perceive three-dimensionally even though their two eyes are medically normal, healthy, and spaced apart in a normal way. Vision that perceives three-dimensional depth requires more than parallax. In addition, the resolution of the two disparate images, though highly similar, must be simultaneous, subconscious, and complete. (After-images and "phantom" images are symptoms of incomplete visual resolution, even though the eyes themselves exhibit remarkable acuity.) A feature article in The New Yorker magazine published in early 2006 dealt with one individual in particular, who, learning to cope with her disability, eventually learned how to see three-dimensional depth in her daily life. Medical tests are available for determining monoptic conditions in humans.