chancellor, premier, prime minister - the person who is head of state (in several countries)

premier, Prime Minister, PM - the person who holds the position of head of state in England

president - the chief executive of a republic

Chief Executive, President of the United States, United States President, President - the person who holds the office of head of state of the United States government; "the President likes to jog every morning"

representative - a person who represents others

crowned head, monarch, sovereign - a nation's ruler or head of state usually by hereditary right