Lateral femoral cutaneous n.

The lateral cutaneous nerve of the thigh (also called the lateral femoral cutaneous nerve) is a cutaneous nerve that innervates the skin on the lateral part of the thigh.

The lateral cutaneous nerve of the thigh is a nerve of the lumbar plexus. It arises from the dorsal divisions of the second and third lumbar nerves. It emerges from the lateral border of the psoas major at about its middle, and crosses the iliacus muscle obliquely, toward the anterior superior iliac spine. It then passes under the inguinal ligament, through the lacuna musculorum and then over the sartorius muscle into the thigh, where it divides into an anterior and a posterior branch.

The anterior branch becomes superficial about 10 cm below the inguinal ligament, and divides into branches which are distributed to the skin of the anterior and lateral parts of the thigh, as far as the knee. 

The posterior branch pierces the fascia lata, and subdivides into filaments which pass backward across the lateral and posterior surfaces of the thigh, supplying the skin from the level of the greater trochanter to the middle of the thigh.