L is a very slim, pale, tall young man with messy neck-length black hair and black eyes. One of his most noticeable features is the shadow below each of his eyes, a result of him being an insomniac.

 L is always shown to be wearing a pair of blue jeans and a long-sleeved white shirt. He almost never wears shoes or socks, preferring to go barefoot, even while in public.

L is quite secretive, very intelligent, extremely meticulous and analytical, has a dry sense of humor, and a love for sweets.