What is the last name of Matty B?

There are two rappers who used a similar name.

Barrett is the last name of "Matty B."

Specifically, Matty B is the performing name of Matthew Barrett. Matty B is a well-known rapper from Western Australia. He first made his mark in rap music as a member of Perth's Syllaboliks hip hop group.

Morris is the last name of young US rapper "MattyB" (aka MattyBRaps, born January 6, 2003).