- "This is me, Eliza Thornberry, part of your average family. I've got a dad, a mom, and a sister. There is Donnie - we found him. And Darwin, he found us. Oh yeah, about our house - it moves, because we travel all over the world. You see, my dad hosts this nature show, and my mom shoots it. Okay, so we're not that average. And between you and me, something amazing happened... and now I can talk to animals. It's really cool, but totally secret. And you know what? Life's never been the same."
- ―Eliza's opening narration at the start of every episode
Elizabeth "Eliza" Thornberry is the main character of The Wild Thornberrys. She is the second daughter to Sir Nigel and Marianne Thornberry and sister to Debbie Thornberry. She also has an adopted brother named Donnie. She is a 12-year-old tomboy who enjoys adventures. Her natural curiosity means she often misjudges a situation and lands her in sticky situations. However, she has the ability to talk to animals, the ability that gave her a best friend in the form of Darwin.
Eliza Thornberry loves animals and exploring the wild jungles, deserts and forests that she travels to along with her family as they film their nature television show (Sir) Nigel Thornberry's Animal World all around the world. What her family doesn't know is that she was given the ability to talk to every animal she meets by a shaman in Africa! Eliza's "Gift of Gab" is a secret. If anyone ever found out what she was able to do, she would lose her powers. It isn't easy for a young girl to keep such a big thing to herself, but luckily she has her best pal Darwin to confide in. Eliza has saved numerous animals from poachers, trappers, and other perilous situations, and never fails to make new friends, no matter what species they may be from.
While other kids her age are studying grammar, Eliza learns about lions who find humans rather tasty. A little too smart for her own good, this determined kid has an awesome secret. A run-in with a local African healer left her with the ability to talk to animals-in their language! Unfortunately, Eliza sometimes forgets that not all animals are as friendly as others. And whether she's saving the day or saving her own skin, life is never dull for Eliza Thornberry.
- According to character design supervisor Patrick Dene, Eliza grows up to host her own wildlife show.