Tunisia is a country in Northern Africa bordering the Mediterranean Sea. Neighboring countries include Algeria and Libya. The geography of Tunisia is varied and consists of mountains in the north and semiarid south that merges into the Sahara. The government system is a republic. The chief of state is the President and the head of government is the Prime Minister. Tunisia has a mixed economic system in which there is a variety of private freedom, combined with centralized economic planning and government regulation. Tunisia is a member of the African Union (AU) and Council of Arab Economic Unity (CAEU).