Alison Lauren "Ali" DiLaurentis is a fictional character in the Pretty Little Liars novel series, introduced in the original series of novels and also appearing in the television adaptation. In both the beginnings of books and television series, Alison is a central character who is shown mostly in flashbacks. The entire plot of the series begins when Alison mysteriously disappears and leaves the small town of Rosewood in shock. Due to her position as a queen bee of Rosewood's social scene, Alison's actions and relations and constantly under scrutiny from the town's citizens. Sasha Pieterse, who portrays the character on screen, has described Alison as an indecisive person, even showing herself as a ruthless, manipulative girl.
Throughout the first three seasons of the television series, DiLaurentis mostly appears in flashbacks and hallucinations. The character plays a more prominent role from the fourth season onwards. In the novel series, Alison's the main antagonist, while on screen she changes her actions and turns out to be a victim too. Alison was the main antagonist for a portion of the fifth season of the television series, when she began working against the Liars. Alison returned to being a protagonist by the end of the season, when she was arrested for Mona's murder and the Liars were kidnapped by A.