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 a 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 League of Arab States (Arab League).