Masashi didnt give him a last name because he isnt one of the main character!
^-^

well, i'm a real deidara fan and i am sure he does not have a last name. masashi kishimoto didn't give him a last name.

I don't think he have a last name...

like what Hidanfan said, he doesn't have a last name. The only akatsuki members who have last names are Itachi and Kisame.

im pretty sure he doesnt have one as well but some ppl think its Iwatoshi!!!! but im not exactly sure if he does or not!!!!

idk