Sopor is a condition of abnormally deep sleep, similar to a stupor but not as severe, from which it is difficult to rouse a person.^[1] It involves a profound depression of consciousness, which is manifested by drowsiness, while maintaining coordinated defensive reactions to stimuli such as pain, harsh sound, and bright light, and preserving vital functions. Sopor may be caused by a drug; such drugs are deemed soporific. A stupor is more severe than a sopor.

The name is derived from Latin sopor (cognate with the Latin noun somnus and the Greek noun ὐπνος, hypnos).

Soporous states can be caused by traumatic, vascular, inflammatory, neoplastic, and toxic lesions of the brain.

Symptoms include lack of response to the environment and inability to perform any tasks or respond to questions. The ability to swallow is maintained. Examination will reveal decreased muscle tone of the extremities and depression of tendon reflexes. Pupillary reaction to light may be sluggish, but the corneal reflexes are preserved. Paresis and Babinski sign may be present.