who is a in pretty little liars?

best answer
Of course Pretty Little Liars eventually had to reveal the identity of A and whilst others characters would don the mantle in later series the original A was revealed to be Mona Vanderwaal played by Janel Parrish (To All The Boys Ive Loved Before). Mona states her reasons for taking on this alias was due to bullying from former clique leader Alison who refused to let her be part of their group.