source for many of these monarchs are the chronicles of the island maint-
ained by monks, known as the Dipavamsa, Mahavamsa, Chulavamsa and the 
Rajaveliya. This list should be used with the following factors kept in mind. 
Firstly the dates provided for the earliest monarchs are difficult to objectively 
verify; those which are particularly difficult to know have been denoted with 
a (?) mark. Secondly in terms of succession it is difficult to divide the mona
rchs into 'houses' or 'dynasties' as often the throne was passed around 
amongst related individuals within a particular clan; especially in medieval 
times there were no articulated rules of succession and whoever was in 
possession of the sacred Tooth Relic had a good claim to being called king, 
which was around the times of the Kingdom of Polonnaruwa to the Kingdom 
of Kandy. Thirdly the list only includes monarchs who had possession of most 
of the island and the power at any one time, therefore monarchs from kingdoms 
and sub kingdoms such as Ruhuna, Maya Rata, Dhakkinadesa and the Jaffna 
kingdom are not on this list. Also the island of Sri Lanka has been invaded by 
many foreign powers over its 2500 year history, mainly from South India, and 
some even seizing the throne making the island part of its empire. Most not
able is the Cholas in 985 and British in 1815. The Portuguese and the Dutch 
however did not seize the Kandyan throne but only occupied territory within 
the island.
Source : Wikipedia The Free Encyclopedia