Which country's flag shows an eagle perched on a cactus devouring a serpent? Mexico. Mexico’s flag places its national emblem—a bird, cactus, and serpent—in the center of its vertical green, white, and red tricolor.
The emblem is linked to the Mexica account of the founding of Tenochtitlan, the city that became Mexico City. According to the familiar version of the story, the Mexica were instructed to settle where they saw an eagle on a prickly pear cactus, eating a serpent. The cactus grew from a rocky island in a lake, identifying the destined site.
The image carries layers of meaning. The eagle is associated with the sun and the deity Huitzilopochtli, while the cactus evokes the place-name Tenochtitlan and the landscape of the Valley of Mexico. Oak and laurel branches frame the emblem on the official coat of arms.
A subtle complication is that surviving pre-Hispanic sources do not consistently show a serpent; some depict the eagle alone or holding another symbol. Modern official versions nevertheless clearly show the serpent, making Mexico the canonical quiz answer.