In the creation and criticism of fictional works, a character flaw or heroic flaw is a bias, limitation, imperfection, problem, personality disorder, vice, phobia, prejudice, or deficiency present in a character who may be otherwise very functional. The flaw can be a problem that directly affects the character's actions and abilities, such as a violent temper. Alternatively, it can be a simple foible or personality defect, which affects the character's motives and social interactions, but little else.

Flaws can add complexity, depth and humanity to the characters in a narrative. For example, the sheriff with a gambling addiction, the action hero who is afraid of heights, or a lead in a romantic comedy who must overcome his insecurity regarding male pattern baldness are all characters whose flaws help provide dimension. Perhaps the most widely cited and classic of character flaws is Achilles' famous heel.

In general, flaws can be categorized as minor, major, or tragic.