Secret identities

As a part of having an alter ego, characters try to keep secret identities, often telling as few people as possible about their alternate identity. Below are lists of characters' secret identities, and who is aware of them.

Barry Allen/The Flash
After waking up from a coma, Barry Allen discovered he'd gained the power of super-speed. Using this to his advantage, he eventually decided to become a guardian angel of Central City. The three S.T.A.R. Labs members that took care of him when he was unconscious decided to work with him.
 * 1) Eobard Thawne: One of the three S.T.A.R. Labs members that looked after Barry during his nine-month comatose state, however, Eobard already knew Barry would eventually become The Flash, as he is from the future and is the Reverse-Flash, the man who murdered Barry's mother.
 * 2) Caitlin Snow: She helped look after Barry during his nine-month comatose state.
 * 3) Cisco Ramon: He helped look after Barry during his nine-month comatose state.
 * 4) Oliver Queen: Before actually becoming The Flash, Barry consulted Oliver on what to do. Oliver motivated him to become The Flash, observing his super speed as he ran away.
 * 5) Joe West: Before Barry was shot by Clyde, Joe shot Clyde himself numerous times. He shortly discovered that Barry had been given his powers from the bolt of lightning that had struck him.
 * 6) Felicity Smoak: When Felicity visited Barry in Central City, he showed her his newfound abilities.
 * 7) Bette Sans Souci: After saving her from General Eiling, Barry reveal his identity to Bette and he's a Metahuman well.
 * 8) Wade Eiling: Eiling witnessed Barry without his mask on after shooting Bette Sans Souci.
 * 9) Tony Woodward: After defeating his childhood bully, Barry put Tony in The Pipeline and revealed himself.
 * 10) John Diggle: A few members of Team Arrow were in Central City on a mission; while waiting for Oliver to return, Diggle and Felicity were talking and The Flash sped up towards them, shocking Diggle (as he previously felt that the speed might have been exaggeration, until he finally saw it with his own eyes.)
 * 11) Lyla Michaels: After coming to Starling City to help out Oliver, Barry accidentally let Lyla know that he was The Flash, assuming Diggle had told her.
 * 12) Roy Harper: Arriving back from getting sushi, Barry kept his mask off but the rest of his outfit on, letting Roy see.
 * 13) Henry Allen: After piecing together a number of interactions with The Flash, Henry concluded that he is Barry. Despite Barry shrugging the accusation off, Henry proceeded to admit how proud he was and assure that, if his son was actually The Flash, that he was doing real good.
 * 14) Ronnie Raymond: He became aware of Barry's secret identity as he met him in S.T.A.R. Labs after the separation of Firestorm.
 * 15) Martin Stein: He became aware of Barry's secret identity as he met him in S.T.A.R. Labs after the separation of Firestorm.
 * 16) Clarissa Stein: Upon seeing Barry using his speed to quickly get her husband a pizza, it is presumed that Clarissa was intelligent enough to link him and The Flash (who was on the news) as the same person.
 * 17) Leonard Snart: Leonard tortured Dante Ramon, forcing Cisco to reveal The Flash's identity in return for his brother's life.

Sara Lance/The Canary

 * 1) League of Assassins: The entire League, including the likes of Ra's al Ghul, Nyssa al Ghul and Al-Owal, were aware of Sara's vigilantism in Starling City, due to her having trained with them.
 * 2) Sin: After saving her from being raped by a group of men, Sara revealed her identity to Sin.
 * 3) Oliver Queen: Oliver trapped The Canary with a bunch of ropes attached to arrows, only to take off her mask to reveal Sara. He in turn revealed his identity.
 * 4) John Diggle and Felicity Smoak: When Sara joined Oliver's team, she met Diggle and Felicity.
 * 5) Quentin Lance: When the League of Assassins began to hunt Sara down, under orders from Nyssa al Ghul, Sara decided that the best way to protect her family was to reveal her secret identity, thus giving them a full idea of the dangerous situation. She revealed this to her father, who was initially shocked at her appearance, though accepting of her actions.
 * 6) A.R.G.U.S.: Amanda Waller and Lyla Michaels were aware of who Sara was and what she did.
 * 7) Roy Harper: When Roy joined Oliver's team, he met its members, among them being Sara.
 * 8) Slade Wilson: When Slade began to hunt down Oliver and destroy him, Oliver's team fought back. In the midst of this, Slade was made aware of Sara still being alive, and further inferred Sara's vigilantism.
 * 9) Laurel Lance: When Laurel saw Sara's injuries after Slade's attack, she was nearly heartbroken on learning this.
 * 10) Caitlin Snow: After Felicity gave her some evidence to process in regards to The Canary's death, Caitlin openly called her "Sara", somehow knowing who The Canary was.
 * 11) Cisco Ramon: As Caitlin openly named The Canary as Sara, either Cisco was already aware of her identity, or he became aware then.

Laurel Lance/The Canary/Black Canary

 * 1) Roy Harper: Roy learned of her identity while stopping a mugger.
 * 2) John Diggle: Diggle learned of her identity after Roy helped her, which led to him finding out quickly.
 * 3) Felicity Smoak: Believing that The Canary was back, but it wasn't Sara, she discovered that it was in fact Laurel.
 * 4) Ted Grant: Ted inferred that Laurel was the Black Canary after watching the news.
 * 5) Oliver Queen: Oliver learned about Laurel's alter ego through his team.
 * 6) Quentin Lance: He was able to assume that Laurel was taking her sister's place as a vigilante while she way away, but later found out that Sara was in fact dead.
 * 7) Thea Queen: She found out after walking into the Foundry and seeing Laurel in costume after the latter was injected with Vertigo.
 * 8) Ray Palmer

Malcolm Merlyn/The Dark Archer

 * 1) League of Assassins: The entire league, including Ra's al Ghul, Nyssa al Ghul and Al-Owal, are aware of Malcolm's secret identity, and are all unhappy about what he'd done.
 * 2) Oliver Queen's team: Following Malcolm's reveal to The Hood about him being The Dark Archer, Oliver's entire team is aware of Malcolm's alter ego, like Oliver Queen, John Diggle, Felicity Smoak, Laurel Lance, Sara Lance and Roy Harper.
 * 3) Tommy Merlyn: As they were being shot at by members of the Chinese Triad, Malcolm revealed his panic room to Tommy, fully equipped with his Dark Archer suit and equipment.
 * 4) Moira Queen: As they were both high ranking members of Tempest, it is unconfirmed but implied that she is aware of this secret.
 * 5) Thea Queen: As Thea was about to be attacked by one of Slade Wilson's army, Malcolm intervened and pulled off his mask to reveal his identity to her.
 * 6) Danny Brickwell: After Merlyn tracked down Brickwell and prepared to avenge his wife, he revealed his own identity during the confrontation.

Oliver Queen/The Hood/The Arrow
Oliver initially acted as a vigilante known as The Hood. However, a year later he began to be known as a hero, The Arrow.
 * 1) Lodai: Since Lodai is Oliver's supplier for all of his vigilante equipment and activities, it is very likely that he is aware of Oliver's secret identity.
 * 2) John Diggle: Oliver was forced to reveal his identity as The Hood when Diggle was shot by Deadshot, and had to recuperate in Oliver's base after being given medicine. Dig initially did not accept Oliver's vigilantism, but later was accepting and joined Oliver's vigilante team.
 * 3) Derek Reston: After saving his son, Derek was shot, and in his dying moments Oliver decided to reveal his identity to him, to prove that the always had his best interests at heart.
 * 4) Helena Bertinelli: After Oliver realized that Helena was The Huntress, he helped save her, and she in turn discovered The Hood's identity. Helena joined Oliver's team, helping to fight crime, however she was too blinded by her hatred for her father, and left.
 * 5) Felicity Smoak: Following Oliver being shot by Moira Queen when he tried interrogating her, he lay in the back of Felicity's car with a wound. He revealed his identity to her, and the two of them drove to Robert Queen's warehouse, where Oliver's base lay beneath. Once there, Felicity and Diggle operated on him.
 * 6) Tommy Merlyn: When his father, Malcolm, was shot by Deadshot, Oliver revealed his identity to Tommy in order to trust him to save his father's life. Tommy was conflicted over Oliver's revelation and often argued with him over his actions, though Tommy ultimately kept the secret.
 * 7) Webb: After trying to stop the production of Vertigo, Oliver was drugged with it and knocked out. He was strapped down, only to escape and kill Dr. Webb.
 * 8) Webb's accomplice: When Dr. Webb trapped Oliver, the two of them learnt his true identity. He was ultimately killed by John Diggle when he escaped.
 * 9) Malcolm Merlyn: Oliver went after Malcolm, who revealed his identity as The Dark Archer. Malcolm ultimately won the fight, pulling off Oliver's hood in shock.
 * 10) Sara Lance: For over a year Sara suspected Oliver to be The Hood, later The Arrow, and she finally discovered that her suspicions were true when her identity was revealed to Oliver. She joined Oliver's team not long after that.
 * 11) Al-Owal: Al-Owal broke in to the Queen Mansion while Sara was staying there. Not only did he know of her whereabouts, but he also knew of Oliver's alter ego, The Arrow. It's possible he knew it due to Malcolm, his former protégé, knowing it.
 * 12) A.R.G.U.S.: Some members of A.R.G.U.S., including the likes of Amanda Waller and Lyla Michaels, are aware of Oliver's secret identity, as well as his associates, John Diggle and Felicity Smoak.
 * 13) Count Vertigo: Count Vertigo was able to deduce Oliver's identity as The Arrow solely due to his large connection to Felicity Smoak, who also had a large connection to The Arrow. He used his knowledge of this connection to lure Oliver to Queen Consolidated, where Oliver confirmed his ideas of Oliver's identity, only to be killed when Count Vertigo almost killed Felicity.
 * 14) Barry Allen: Felicity and Diggle made the call to reveal Oliver's secret identity to Barry when Oliver was poisoned by unknown chemicals from an A.R.G.U.S. disaster bunker, following his fight with a Mirakuru-enhanced Cyrus Gold. Oliver was annoyed at this, though soon came to terms with it and accepted Barry.
 * 15) Slade Wilson: For the entire time that Oliver acted as The Hood, then The Arrow, Slade had figured that he was indeed Oliver, due to the green hood's significance - a reference to that of Yao Fei's and Shado's hood. He made it his sole purpose to destroy Oliver's life and reverse his heroic deeds.
 * 16) League of Assassins: The entirety of League of Assassins, including the likes of Ra's al Ghul, Nyssa al Ghul and Maseo Yamashiro who know about Oliver as The Arrow.
 * 17) Roy Harper: Oliver was forced to reveal his secret identity to a Mirakuru-enhanced Roy in order to calm him down, to stop him from beating Ben Turner to death. Roy later joined Oliver's team, but left the team, because he (correctly) blamed Oliver for Thea getting kidnapped by Slade Wilson.
 * 18) Isabel Rochev: Due to being in league with Slade Wilson, a fact which she eventually revealed to Oliver, Isabel was aware of Oliver being The Arrow.
 * 19) Laurel Lance: When Slade Wilson began publicly ruining Oliver's life, he turned up at Laurel's door to tell her of Oliver's identity as The Arrow. Laurel was initially shocked and began to add up the clues, but after advice from her father, decided that it was best to not approach Oliver about it and allow him to do his job.
 * 20) Moira Queen: Whilst having a conversation about Thea, Moira also revealed to Oliver that she had figured that Oliver was the vigilante since around the events of The Undertaking, and before Oliver could say a thing, Moira expressed that she couldn't be prouder.
 * 21) Sebastian Blood: When having dinner, Sebastian was joined by Oliver who started a conversation about Slade Wilson before saying “I'm the Arrow”. Sebastian didn't seem overly suprised at the discovery.
 * 22) Harrison Wells: After The Arrow and his team came to Central City to help The Flash and his team, Harrison wished to learn The Arrow's identity in order to put his faith in him, though Felicity reasoned that it wasn't her secret to tell. However, he was later able to simply guess who he was to Felicity.
 * 23) Joe West: Harrison was able to simply guess The Arrow's identity in front of him, Felicity confirming it as she was at the point of no return in regards to denial.
 * 24) Caitlin Snow: Harrison was able to simply guess The Arrow's identity in front of her, Felicity confirming it as she was at the point of no return in regards to denial.
 * 25) Cisco Ramon: Harrison was able to simply guess The Arrow's identity in front of him, Felicity confirming it as she was at the point of no return in regards to denial.
 * 26) Thea Queen: Oliver revealed his identity after he decided that it was safer if she knew, what with the threat of Ra's al Ghul.
 * 27) Ray Palmer: He tracked down The Arrow and used his helmet's x-ray vision to see Oliver's face.

Slade Wilson/Deathstroke

 * 1) Sebastian Blood: After Sebastian failed to stop Oliver and Laurel from finding a file on his father, Slade became angry, killing multiple guards and pulling off his mask to reveal himself.
 * 2) Oliver Queen: When he went to Amanda Waller, Oliver was told about Deathstroke. He made the connection soon enough that Slade was the masked vigilante.
 * 3) Oliver Queen's team: Although offscreen, it is presumed that Team Arrow (Sara Lance, John Diggle, Felicity Smoak, and Roy Harper) were told about Deathstroke by Oliver.
 * 4) A.R.G.U.S.: The entirety of A.R.G.U.S., including the likes of Amanda Waller and Lyla Michaels, were not aware of Slade's secret identity, Deathstroke, until Oliver told Amanda that Slade is alive. After this she quickly figured out that the mercenary that they had codenamed Deathstroke is Slade.
 * 5) Isabel Rochev: As they were part of the Church of Blood together, it was presumed Isabel was aware of Slade being Deathstroke.
 * 6) Laurel Lance: In the underground Church of Blood base, it is unknown but confirmed that Laurel found out about Slade.
 * 7) Quentin Lance: After the masked man was shown on screen, The Arrow called Quentin to arrest Slade Wilson. Quentin then figured out that Slade is Deathstroke.
 * 8) League of Assassins: The entire league, including Nyssa al Ghul, are aware of Slade's secret identity; they learned this through Sara Lance.
 * 9) Malcolm Merlyn: It is unknown but confirmed that Malcolm found out about Slade.

Sebastian Blood/Brother Blood

 * 1) Daily: As he was part of the Church of Blood, Daily was aware of Sebastian being Brother Blood.
 * 2) Cyrus Gold: As he was a childhood friend of Sebastian as well as part of the Church of Blood, Cyrus was aware of Sebastian being Brother Blood.
 * 3) Slade Wilson: As he is the leader of the Church of Blood, Slade is aware of Sebastian being Brother Blood.
 * 4) Isabel Rochev: As she was part of the Church of Blood, Isabel was aware of Sebastian being Brother Blood.
 * 5) Laurel Lance: Laurel first suspected Sebastian when she was investigating him after the death of Lucas Hilton. Later on, when she found out Sebastian wrote a press statement about Moira Queen's death, she learned that Sebastian was Brother Blood.
 * 6) John Diggle: Diggle learned through Laurel that Sebastian was Brother Blood.
 * 7) Felicity Smoak: Felicity learned through Laurel that Sebastian was Brother Blood.
 * 8) Oliver Queen: Oliver learned through Laurel that Sebastian was Brother Blood.
 * 9) Clinton Hogue: As he is Sebastian's former bodyguard, Clinton was aware of Sebastian being Brother Blood.

Roy Harper/Arsenal

 * 1) Oliver Queen's team: After Roy joined the team (during that time the members were; Oliver Queen, John Diggle, Felicity Smoak, and Sara Lance), they all became aware of his secret identity as he helped fight crime with them.
 * 2) Laurel Lance: When Laurel joined Team Arrow, she discovered Roy's identity.
 * 3) Nyssa al Ghul: When Nyssa temporarily joined Team Arrow, she became aware of Roy's identity.
 * 4) Barry Allen: When visiting Starling City to help The Arrow, Barry was allowed into the Arrowcave, thus becoming aware of Arsenal's identity.
 * 5) Caitlin Snow: When visiting Starling City to help The Arrow, Caitlin was allowed into the Arrowcave, thus becoming aware of Arsenal's identity.
 * 6) Cisco Ramon: When visiting Starling City to help The Arrow, Cisco was allowed into the Arrowcave, thus becoming aware of Arsenal's identity.
 * 7) Thea Queen: Thea was able to deduce that Roy was the red-hooded counterpart to The Arrow.
 * 8) Quentin Lance: Quentin was able to make the connection between Roy's red hoodie and working with the Arrow, therefore concluding him as Arsenal.

Ted Grant/Wildcat

 * 1) Isaac Stanzler: Isaac was aware of Ted's secret identity, as he was once the latter's partner and protégé.
 * 2) Oliver Queen: After Oliver got into a confrontation with Ted, the latter confess to Oliver that he used to be a vigilante.
 * 3) John Diggle: Diggle learned through Oliver about Ted's former vigilantism.
 * 4) Felicity Smoak: Felicity learned through Oliver about Ted's former vigilantism.
 * 5) Roy Harper: Roy learned through Oliver about Ted's former vigilantism.
 * 6) Laurel Lance: Laurel learned through Oliver about Ted's former vigilantism.
 * 7) Starling City Police Department: All members of the SCPD, like Quentin Lance, are aware of Ted's secret identity after they received an anonymous tip that led them to a dead body found in Ted's locker, as well as evidence that he supposedly killed seventeen people, revealing his past as a vigilante. However, the evidences were planted there to frame him for crimes he did not commit, as the tip came from Isaac Stanzler, Ted's ex-partner and former protégé.

Eobard Thawne/Reverse-Flash

 * 1) Wade Eiling: Eiling was abducted by Thawne and taken to the sewer where Grodd resides, and there he unmasked himself to General Eiling.
 * 2) Grodd: When Thawne brought General Eiling to the sewer, he unmasked himself, just before Grodd attacked Eiling.
 * 3) Hartley Rathaway - Hartley somehow knows that Eobard is the Reverse Flash but how and when he discovered this remains unstated.