sacral plexus, a network of motor and sensory nerves formed by the lumbosacral trunk from the fourth and fifth lumbar nerves and by the first, second, and third sacral nerves. They converge toward the lower part of the greater sciatic foramen and unite to become a large, flattened band, most of which continues into the thigh as the sciatic nerve. Compare lumbar plexus. See also lumbosacral plexus.
