The lateral cutaneous nerve of thigh (lateral femoral cutaneous nerve) is a sensory branch of the lumbar plexus carrying fibers from the dorsal branches of the ventral rami of L2 and L3.  It emerges through the lateral aspect of psoas major, above the level of the inguinal ligament, distal to the site of emergence of the femoral nerve.  It passes infero-laterally across iliacus, runs deep to (or sometimes through) the inguinal ligament to enter the upper part of the thigh, just medial to the anterior superior iliac spine.  In the antero-lateral part of the thigh it passes through or anterior to the sartorius muscle, where it divides into anterior and posterior divisions.  The anterior division gives off branches to the skin of the anterior and lateral thigh, and terminates by joining with the cutaneous branches of the anterior division of the femoral nerve and the infrapatellar branches of the saphenous nerve.  The posterior division terminates in the skin on the lateral surface of the thigh.

 Supply
The anterior branch supplies skin of the anterior and lateral thigh and makes a contribution to the patellar plexus; the posterior branch supplies skin on the lateral surface of the thigh as well as gluteal skin.