who is a in pretty little liars?

Mona is A, but I am talking about the books, not the TV show. Mona is A in the first 4 books (Pretty Little Liars-Unbelievable) and then Spencer accidentally pushed her off a cliff (Mona was strangling her). But in the 2nd part of the book series (Wicked-Wanted) it explains that Ali had a twin sister, Courtney, who was in a mental hospital. Courtney pretended to be Ali so that Ali would go to the mental hospital. So Courtney actually died, not Ali. So then Ali was never friends with Spencer, Aria, Hannah, and Emily. Ali was mad that Courtney pretend to be her and that she became friends with them. She wanted to still be friends with Naomi and Riley because the real Ali thought that Spencer, Aria, Hannah, and Emily were losers. So Ali became the A in those books. She brought the Pretty Little liars to her house in the Poconos where she kept the dead body of Ian (in a closet where Spencer's sister Melissa was held Prisoner). Ali then set the house on fire, but the Pretty Little Liars escaped, but the real Ali dies. I actually wrote this myself, with my knowledge of the books, but you can go on Wikipedia and search "Pretty Little liars" and it gives you a summary of each book. Hope this helped you!!!! :)

-A ;)

I think It could be Aria. I know it seems very unlikely but she suffers with schizophrenia which is a mental disorder where someone has more than one personality and may not know the other side exists. She could be 'A' and might not know it. Throughout the series she has had many different phones which is quite strange. That could just be a coincidence but it might not be. Also on the most recent episode Aria says 'Somebody we don't know' and Hanna replies 'Or someone we would never expect' and as she says it,the camera pans out to Aria. In season 2, Mona even refers to Aria as “Big A” while trying to catch up with her in their high school hallways. In the season 2 finale, the girls are on the hunt for the “Black Swan” at the masquerade ball after seeing a sketch of the costume in 'A’s' lair. Eventually, we find out Melissa was the one behind the mask – but that 'A' told her to wear it. Coincidentally (or not?), Aria is dressed-up in a red and black striped gown at the soiree, a dress that strangely resembles an old Black Swan poster. Also in the season 2 finale, just before Mona is revealed as the first 'A,' viewers get a glimpse of a dollhouse in the creepy lair. Inside? Dolls representing each of the girls. Ali’s doll, which is strategically placed above the other dolls, is rocking a crown. The other girls’ counterparts are adorned in threads that match what they wear day-to-day. Aria’s doll however, is outfitted in a black 'A'-esque hoodie. Weird.

I have this theory. On a Pll interview Keegan Allen said that if you pay verry close attention on season one, you can find out who A is. On the season finale on season 5, it showed Charles DiLaurentis, who is Jason's fraternal twin, who was also jealous of Alison for being beautiful. I replayed the whole season 1 many times. If you go to episode 3 of season 1, minute: 32:15, you will see a blonde male that could possibly be Charles DiLaurentis. Now, this is just a theory which could be totally WRONG. so just tell me what you think.

Charles Dilaurentis

Charles

CeCe Drake is A, Otherwise known as Charles DeLaurentis

Everyone says Mona is A, she's not , she was originally apart of the "group" but she left. Charles DeLaurentis is A , he is the twin of Jason, Mrs. D, never told Charles that he was a boy, he made him think he was a girl, and I think that Charles found that out , got mad and wanted revenge.

They confirmed it in the previous episode that CeCe Drake is A. (a.k.a. Charles Di laurentis, AND Charlotte) And Sara Harvey is red coat AND black widow.

Cece drake

In the Show Charles

In the Books Courtney.