From the Wikipedia page 
Masasi is one of the six districts of the Mtwara Region of Tanzania. It is bordered to the North by the Lindi Region, to the East by the Newala District, to the South by the Ruvuma River and Mozambique and to the West by Nanyumbu District.
Masasi District Profile Masasi District Council is among seven Councils comprising Mtwara Region.
The Council has Five (5) administrative divisions, Twenty three (23) wards and 159 villages and 864 hamlets with total area of 3,829.9 sq km and the physical size is 20.8% of the whole Region. Administratively Masasi is divided into two constituencies which are Masasi and Lulindi. The Council has a total of 31 Councillors.