Saint Lucia, part of the Lesser Antilles, is an island country in the Caribbean Sea. Proximate countries include Saint Vincent and the Grenadines, Barbados, and Dominica. The geography of Saint Lucia is volcanic and mountainous. The government system is a parliamentary democracy and a Commonwealth realm; the chief of state is the queen of the United Kingdom, and the head of government is the prime minister. Saint Lucia has a mixed economic system in which there is a variety of private freedom, combined with centralized economic planning and government regulation. Saint Lucia is a member of the Caribbean Community (CARICOM) and the Organization of Eastern Caribbean States (OECS).