Leah Birch is a supporting character in Big Mouth. She is the daughter of Elliot Birch and Diane Birch, the younger sister of Judd Birch and the older sister of Nick Birch.

Leah is a tall and slim Caucasian teenage girl with long tailbone-length blonde hair that is styled on either side with a butterfly clip in that has a magenta body and tangerine wings on the right side of her head, sky blue eyes, blonde eyebrows and lemonade lips.