In human anatomy, the palmar or volar interossei (interossei volares in older literature) are four muscles, one on the thumb that is occasionally missing, and three small, unipennate, central muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers.

The tendons of these three muscles pass posterior to the deep transverse ligament before being inserted onto the extensor expansion.

All three intrinsic groups of muscles pass palmar to the axis of the metacarpophalangeal joints, and therefore contribute to flexion there.

[8] The pollical palmar interosseous muscle (PPIM) is absent in non-human primates, and is probably an autapomorphic muscle unique to the human thumb (together with flexor pollicis longus) which probably evolved from the oblique portion of adductor pollicis.

The insertion of the PPIM into the extensor mechanism is likely to have evolved with tool usage in early hominids.