Bonzo Madrid is a character in the fictional novel Ender's Game, by Orson Scott Card. Bonzo is a supporting character, serving to bring out Ender's brutal nature while at Battle School.

Bonzo is allegedly from a wealthy family in Spain, sent to Battle School. Bonzo is first Ender Wiggin's commander; Bonzo hates him bitterly because of his young age. When Ender disobeys Bonzo's rule against participating in team battles, Ender leaves Bonzo's "army." Later, Bonzo and several of the older adolescents plot to gang up on Ender while in the showers.

Ender is trapped by Bonzo and his cronies. Bonzo and Ender end up engaging in single combat, because Ender uses his great Spanish honor against him. By turning on the hot water faucets, Ender is able to evade Bonzo. Ender smashes his head into Bonzo's nose, which in turn pierces his brain and kills him. Bonzo is sent home to his family travelling in a bag, ironically on the same shuttle at the same time as Ender was taking his short leave back to Earth.

The Bonzo incident is pivotal in Ender's development, as it gave Ender a feel of true desperation and emergency. Ender does not believe he wanted to kill Bonzo, but was forced to given the circumstances. Leading up to this, Colonel Graff was determined to isolate Ender so that when Ender finally was placed in battle against the Formics, he would feel he must succeed alone. Despite this goal, Graff did not intend to endanger the life of a student of the Battle School. By forcing Ender to take on Bonzo alone, without any adult intervention, Graff made a mistake that stayed with him through the rest of his career, one he continued to think of when making future decisions, and validating his own work.