What are supporter of shi'ahs called

The supporters of shi'ahs are called Shiites.

Explanation:

The religion of Islam has been bifurcated into two broad divisions. These divisions are of Sunni Islam and Shia Islam.

The followers of Sunni Islam believe that a friend of Muhammad named Abu Baker was chosen as his scion after the death of Muhammad.

The Shia's contradict with that proposition and believe that the nephew of Muhammad was chosen to take the responsibility of taking Islam forward.