A


 * -| Mona=

The original and first "A", who became "A" initially to get back at Alison but started back up out of fear of losing Hanna.
 * -| Lucas=

Lucas was Mona's helper in her game. He is the "A" who massaged Emily for Mona and later performed deeds for the A-Team. He claims it was because of blackmail.
 * -| Toby=

A member of the "A-Team", who was recruited by Mona when he got his job in Bucks County. He claims he joined in order to protect Spencer.
 * -| Spencer=

A member of the "A-Team", Spencer joined in order to find answers on her seemingly deceased boyfriend Toby. She kidnapped Malcolm Cutler to prove herself to Mona and worked as a spy as well. However, upon realizing that Toby is alive, she becomes a double agent.
 * -| Wilden=

Wilden was tasked to be the "Queen of Hearts" along with Melissa, and his purpose was to get rid of the Liars on the Halloween train, but he evidently failed. He was murdered by Charlotte DiLaurentis after he betrayed her.
 * -| Melissa=

When Mona was "A", Melissa was forced to dress-up in a costume known as the "Black Swan" and go to the masquerade party to distract Aria, Emily and Hanna, otherwise her secret (that she was faking a pregnancy) would be exposed. Afterwards, Melissa was tasked to be the "Queen of Hearts" along with Wilden on the Halloween train. Melissa claimed that she didn't want to do it and Wilden told her what to do.
 * -| Charlotte=

The second main "A" and Red Coat, Charlotte became "A" to get out of Radley and get closer to her family; however, her other motive is because Mona told her the Liars were happy that Alison was gone. Her later motive was having an addiction to the game. She was soon murdered in 2017 by an unknown assailant. Charlotte is notably the most dangerous "A".
 * -| Sara=

Sara was first found held captive in "A"'s Dollhouse, later befriending Emily Fields and developing a romantic relationship with her, due to their experiences together in the Dollhouse. However, Emily was left ultimately betrayed when it was revealed Sara was actually Charlotte's helper, as well as Red Coat and the Black Widow, and she got close to Emily to help Charlotte with the game. It was never revealed why she helped Charlotte before her murder.
 * -| Noel=

Five years after Charlotte was revealed to be Big "A", it was unveiled that Noel Kahn had assisted her in the Dollhouse she built to kidnap and torture the Liars in. It is currently unknown if he was forced to do it, if he wanted to, or what his motivations are. Noel was killed by Emily Fields in "The DArkest Knight" when he and Jenna attempted to murder the Liars with an axe. Emily fought back, causing him to drop the axe and be knocked to the ground, decapitating himself on the axe.
 * -| Jenna=

Jenna is Uber A's helper and also wants to avenge Charlotte, as well as getting revenge on the Liars for blinding her. She initially works for Uber A anonymously, but seemingly knows their identity after they rescue her, and is currently helping them complete their final endgame.
 * -| Uber A=

Whilst the identity of Uber A is currently unknown, Uber A wants to avenge Charlotte's death by finding the killer and taking it into their own hands. They believe one of the Liars knows the truth and will stop at nothing to get what they want. They are the third main "A".

"A" is the main antagonist of the Freeform original series "Pretty Little Liars". They are an anonymous Big Bad that target the main characters, the Liars, for their own motive and will stop at nothing to get what they want.

While there have been multiple of them, the original and first main "A" was revealed in the second season finale to be Mona Vanderwaal, the Liars' ally. Her helper was Lucas Gottesman. When Mona is sent to Radley Sanitarium for treatment, she is approached by an unknown person who wants to form a partnership, and that person becomes the second main "A", known as Big "A".

Mona and Big "A" form the "A-Team", hiring Toby Cavanaugh, Spencer Hastings, Darren Wilden and Melissa Hastings. After Toby and Spencer leave the team, Big "A" steals the game from Mona and kicks her out of the team, where she becomes one of the Liars herself. Big "A" gains their own personal helper and the "A-Team" disbands after they murder Wilden for betraying them and Melissa leaves. In the 6A finale, Big "A" is unmasked as CeCe Drake, who is actually Alison DiLaurentis' older sister, Charlotte DiLaurentis, with her helper being Sara Harvey. The two of them were Red Coat. In Season 6B after the five year jump, Charlotte is murdered and this spawns the birth of the third main and final "A", known as Uber "A", who wants to find her killer and get revenge. They hire Jenna Marshall and others as their helpers. In Season 7, it was revealed that Charlotte had a second helper, who was Noel Kahn.

Even though Ezra Fitz and Shana Fring were not members of the "A-Team", they were a type of "A" in their own rights.

History
In October 2008, Mona Vanderwaal began sending Alison DiLaurentis anonymous threats. Mona sent Alison dolls and stalked her and the Liars, while wearing a zombie baby costume. On Halloween night, Mona attacked Alison, who believed she was Noel Kahn, and crowned herself as "A". Mona's threats as "A" grew stronger and darker and Alison became fearful. On Labor Day weekend of 2009, Mona began sending Alison murder threats to scare her. Various angry people were in Alison's yard and Alison ended up getting hit with a stone by CeCe Drake, who thought she was Bethany Young. Mona, in turn, hit Bethany, believing her to be Alison. Alison survived the incident and was found by Mona on the side of the road, who then convinced her to disappear. Mona finally had everything she wanted and became best friends with Hanna Marin, with both of them becoming the Queen Bees of Rosewood High. Alison's disappearance drew her friends apart and Aria moved away to Iceland. A year after the disappearance, Aria returned to Rosewood and Mona feared that she would lose Hanna to them. So in order to keep them apart, she began using "A" again. She hired help from Lucas Gottesman, blackmailing into being her helper. However, Mona's plan backfired when she actually ended up bringing them closer together. This made Mona even angrier and she eventually began pretending to receive threats from "A" herself. Gaining the Liars trust, Mona began working with them and she and Spencer went out to the Lost Woods Resort to find a clue on "A". Mona ends up revealing herself as "A" to Spencer and tries to convince Spencer to join the A-Team. Meanwhile, at the Ball, the other Liars follow Melissa Hastings, who Mona sent to the Ball, dressed anonymously as the Black Swan. Mona and Spencer fight and Mona ends up falling off of a cliff, but she survives and is admitted to Radley Sanitarium. Here, CeCe Drake begins visiting her and Mona tells her all about the "A" game. CeCe offers her a partnership and they become "A" together, starting a full A-Team, which consists of Toby Cavanaugh, Spencer Hastings, and a blackmailed Lucas and Melissa again. CeCe begins to believe that her cousin and adoptive sister, Alison, is alive and begins disguising herself as Red Coat. She hatches a plan to draw Alison out and forms an alliance with Sara Harvey, who she sends to act as a decoy Red Coat on the night of the Thornhill Lodge party. Their plans are foiled when Shana Fring sets the Lodge ablaze, but it manages to work, as Alison rescues Hanna from the fire, proving she is alive and the other Red Coat.

Later, Shana was killed by The Liars in self-defense when she attempted to finish the job to kill them. Seeing this as the perfect opportunity to end the game, as the Liars thought Shana was "A", Cece prepared to leave for Paris. However, Cece has an addiction to the game, and decided to stick around. After kidnapping the Liars, and mentally torturing them in a dollhouse, she later kidnapped Alison to explain her story. After finishing, Cece orders Sara to set off a bomb she planted in the building, so that they could die together, but Spencer disbales the bomb, and Emily quickly subdues Sara. Her plans foiled, Cece attempted suicide on the roof, but Alison convinces her to stop, and she declares "Game Over"

Known "A's"

 * Mona Vanderwaal
 * Lucas Gottesman
 * Toby Cavanaugh
 * Spencer Hastings
 * Darren Wilden
 * Melissa Hastings
 * Charlotte DiLaurentis
 * Sara Harvey
 * Noel Kahn
 * Jenna Marshall
 * Uber A

Trivia

 * Big A's identity was revealed to be CeCe Drake.
 * Melissa Hastings and Lucas Gottesman were both revealed to have worked as "A", but both claiming to have been blackmailed.
 * Charlotte and Sara both shared the identity of Red Coat.
 * Sara was the "A" wearing the black veil disguise, which has been nicknamed "The Black Widow" by the writers.
 * Ezra Fitz was believed by the fans and Liars to be Big "A" briefly, before it was revealed that he was instead writing a book on Alison.
 * It is heavily implicated that Mary Drake, Elliott Rollins, Sara Harvey, and Noel Kahn were all working for Uber A at some point. However, only Jenna has been confirmed to be on the Uber A-Team.

Possible "A's"

 * -| Archer=

Archer posed as a man named "Elliott Rollins" and fell in love with Charlotte DiLaurentis, but after she was murdered, he was heartbroken and suspected her adoptive sister Alison of doing it, later possibly becoming a helper of Uber "A". He married her to steal her money, and he worked with her aunt Mary Drake to make her go crazy. She put herself in Welby State Psychiatric Hospital where he worked as her doctor, abusing her for "killing" Charlotte. He was later found out and was accidently ran over by the Liars, being killed in the process, and was buried in a nearby forest.
 * -| Mary=

Mary Drake was revealed as the identical twin of Jessica DiLaurentis, being put in Radley Sanitarium at a young age because of something Jessica did. Mary was eventually released and she spent most of her life wanting to get back to the child she gave birth to in Radley (Charlotte). After finding out Charlotte was murdered, she began thinking Alison did it and assisted Archer Dunhill in stealing her money from the Carissimi Group, and also possibly became Uber A's helper. Mary refused to further assist Archer and redeemed herself.