Hanna Olivia Marin is a fictional character created by Sara Shepard for the Pretty Little Liars book series, and later developed for the Freeform television series adaptation by I. Marlene King. The character has also appeared in the spin-off series Ravenswood.

One of the main leads of the franchise, Hanna is a formerly overweight girl who becomes a queen-bee after the disappearance of Alison DiLaurentis.

Hanna is portrayed by Ashley Benson in the television series.

Hanna is introduced in the first book as a popular and ruthless girl. She is described as an alluring young brunette who occasionally fights with herself to keep her beauty. In early novels, the character is also written as bulimic.

Hanna is one of four primary protagonists in all sixteen Pretty Little Liars novels, starting with Pretty Little Liars. All four girls attend the same school.

Before Alison DiLaurentis disappears, Hanna is shown as a shy girl with an eating disorder. She is best friends with Alison DiLaurentis along with Spencer Hastings, Aria Montgomery and Emily Fields. Like the other girls, Hanna and Alison had a secret between them: Alison witnessed Hanna purging with a toothbrush when she thought she was overweight. During the last night of the 7th grade, while having a sleepover in Spencer's sister Melissa's barn, Alison disappeared.

Years later, in the 9th grade, Hanna tried out for cheerleading but didn't make it, since the cheerleaders considered her too fat and not pretty enough to be in the squad. Hanna and Mona Vanderwaal, a girl that Hanna and her friends used to make fun of for being dorky, decided to become skinny and pretty before next year's cheerleading tryouts. They bonded and became pretty and popular, eventually deciding that cheerleading wasn't even cool enough to try out for. Hanna took over Alison's spot as the most popular girl after Alison's disappearance. Within that time, Hanna and Mona also became shoplifters.

In December 2009, The Futon Critic confirmed the casting of Ashley Benson as Hanna Marin.