A character's ability to make meaningful choices that actually affect the story's outcome, rather than being dragged along by the plot.
Character agency means your character is an active participant in the story, not a passive observer. A character with agency makes decisions, takes risks, and drives the plot forward through their own choices - even if those choices are bad ones. This doesn't mean they control everything that happens to them, but it means they respond to events by doing something rather than having things simply happen to them. The key test is simple: if you removed this character's decisions, would the plot change? If not, they lack agency.
Readers connect with characters who act, not characters who are acted upon. When your protagonist is just reacting to events or being rescued by others, the story starts to feel hollow - like watching someone else play a video game. Agency is what makes readers lean forward and think, 'What are they going to do next?' It's the difference between a character who earns their ending and one who stumbles into it.
Hamlet's agency is famously complicated - his inability to act is itself a choice that drives the tragedy, making inaction a form of agency.
Amy Dunne has terrifying agency. She doesn't just react to her failing marriage - she orchestrates an elaborate scheme that drives the entire plot.
Katniss repeatedly makes active choices - volunteering, allying with Rue, threatening the double suicide - that reshape the games and eventually the political landscape.
Even a child or prisoner can have agency through the choices available to them. Agency is about decision-making, not about winning. A character who chooses wrong still has more agency than one who never chooses at all.
Let your protagonist be the primary solver of their own problems. Supporting characters can help, but the crucial decisions and sacrifices should belong to the main character.
At every major plot turn, ask: is this happening because of a choice my character made, or just because the plot needs it to happen? Restructure if it's the latter.
Take a scene you've already written where something happens to your character. Rewrite it so the same event occurs, but this time your character's own decision - good or bad - is what causes it. Notice how the scene's energy changes when the character drives the action instead of receiving it.