A coup d'état is a sudden and illegal seizure of government power, typically executed by a small group, often military leaders or political factions. The goal is to overthrow the existing government and replace it with a new authority. Coups can occur in various forms, from violent uprisings to more subtle political maneuvers. Historically, coup d'états have been seen in many countries, leading to significant changes in leadership and governance. Notable examples include the 1953 coup in Iran, which replaced Prime Minister Mohammad Mossadegh with Shah Mohammad Reza Pahlavi, and the 1973 coup in Chile that ousted President Salvador Allende.