Thickest nerve in the body is -
The sciatic nerve is the thickest and largest nerve in the body.
The sciatic nerve is the largest branch of sacral plexus and is the largest nerve in the body. It is formed at the lower margin of piriformis by union of its tibial and common peroneal parts.
The main trunk has following branches :


From tibial componentSemitendinosus, semimembranosus, long head of biceps femoris, and ischeal part of adductor magnus.
Common peroneal componentShort head of biceps femoris.


Thus main trunk of Sciatic nerve supplies hamstrings (semitendinosus, semimembranosus, biceps femoris) and ischeal part of adductor magnus.
In the upper angle of popliteal fossa, sciatic nerve divides into tibial nerve and common peroneal nerve.
Trigeminal nerve
Radial nerve
Femoral nerve
Sciatic nerve