Owlman is a character created by DC Comics as an evil counterpart for Batman considering there are breeds of owls that feed on bats. An Earth-2 version was promiently one of the antagonists of the storyline JLA: Earth 2.
In the New 52, Lincoln March is the main antagonist of the storylines City of Owls, Batman Eternal and Robin War as a prime universe version of Owlman as a member of the Court of Owls. An alternate version of Owlman from Earth-3, as a member of the Crime Syndicate, is one of the main antagonists of the event storyline Forever Evil and one of the secondary antagonists in The Darkseid War.
He also appears as the main villain in the animated film Justice League: Crisis on Two Earths and the animated TV series Batman: Brave and The Bold in two episodes, voiced by James Woods and Diedrich Bader respectively.
Owlman first appeared in Justice League of America #29 (August 1964) and was created by Gardner Fox and Mike Sekowsky. In his first appearance, Owlman is an unnamed super-intelligent supervillain who was created as an evil counterpart to Batman and is a member of the criminal organization known as the Crime Syndicate of America who originated and operated on the reverse Earth-Three.
In some of the pre-Crisis Crime Syndicate appearances, the Earth-Three Owlman also somehow has the ability to briefly control other people's minds. When he was knocked out, his subconscious mind was able to activate enough for him to say a word enabling him to travel to Earth-Three. He was also able to see in the dark. In the first travel between Earths, they met the JLA and JSA, but were defeated and imprisoned between Earth-1 and Earth-2 by Green Lantern. Later the time traveling villain Per Degaton released them as part of his plan to take over Earth-2 by stealing nuclear missiles from the Cuban Missile Crisis of Earth-Prime.
When the Syndicate betray him, they are sent to 1982 as he had made sure this would happen when they touched him. When he was defeated, these events were erased from existence. The pre-Crisis Earth-Three Owlman and all members of his Crime Syndicate are killed during the Crisis on Infinite Earths maxi-series at the hands of the Anti-Monitor from a wave of antimatter destroying pre-Crisis Earth-Three.
Justice League of America: Earth 2
This Owlman was developed to be reflective of the modern readers with a darker attitude and background than either of the two previous teams. On antimatter Earth, Owlman was now Thomas Wayne Jr. the older brother of that reality's Bruce Wayne. In most mainstream DC universe, Batman's genesis occurred when young Bruce Wayne was witness to the murder of his parents, Thomas Wayne and Martha Wayne, and was inspired to devote his life to fighting crime.
In the antimatter universe however, young Bruce was killed along with his mother by a policeman when Thomas Sr. refused to accompany him for questioning. Thomas Jr. escaped the crime scene with the hoodlum Joe Chill , whom he considered his hero and grew up to become Owlman. Equipping himself with a utility belt containing technology and weapons similar to those used by Batman along with a drug-enhanced high intellect (devoted to crime rather than serving the law), Owlman became a master criminal and an ally to local crimelord "Boss" Gordon (the antimatter Earth's version of James Gordon).
Later he learned that his father Thomas Wayne Sr. was still alive and had become the chief of police in their world's version of Gotham City , gathering a cadre of police officers who did not give into the rampant corruption which infested their version of Earth. Thomas Jr. blames his father for the deaths of his mother and brother and it is strongly hinted that the main purpose to his criminal career is to punish his father, who is well aware of who he is and is equally determined to destroy his own son; during his visit to the "main" DC Universe, upon discovering the Waynes' grave he states that nothing matters because "He's dead", presumably referring to Thomas Wayne Sr., and actually shows a rare moment of humanity as he kneels in front of the grave.
While Clark Kent as Ultraman is the leader of the Syndicate, Thomas Jr. as Owlman is the real brains behind the group. The working relationship between the two is extremely tense, due to Ultraman's desire to rule the planet through fear and violence clashing with Owlman's more pragmatic desire to allow dissent and rebellion to run rampant (going so far as to funding opposition towards the Syndicate) in order to provide himself and his allies in the Syndicates enemies to fight.
Further complicating things is the fact that Thomas Jr. has carried on a longtime affair with Ultraman's wife, Superwoman. Ultraman has become aware of the affair, but due to Thomas Jr. having undisclosed photographic blackmail material against the villain, he is unable to seek retribution against Owlman for the betrayal.
In JLA: Earth 2, the antimatter Alexander Luthor, a heroic version of Lex Luthor, makes a reference to Owlman's "drug-enhanced" cerebral cortex, although this version of Owlman does not demonstrate any superhuman powers. Presumably, Thomas Jr. merely uses some sort of drug to enhance his mental capacity though it is not specifically stated how powerful his mental powers are or how they are enhanced through such artificial means.
Recently, Thomas Jr. and his antimatter Crime Syndicate allies have appeared in the weekly "Trinity " series, starting with issue #9. The 'Weaponers of Qward' had attacked their Earth, killing millions and tearing apart the landscaped. The Syndicate had kidnapped hundreds of innocent people from all 52 realities, including what appeared to be Jimmy Olsen, but was later revealed to be his anti-mater duplicate. It is unclear if Thomas Jr. allows the JLA to win in order to get the heroes off his source Earth and counterattack after they depart or if he was actually defeated.
In other media
Batman: The Brave and the Bold
Owlman appears in the Batman: The Brave and the Bold episodes "Deep Cover for Batman" and "Game Over for Owlman" as the main antagonist. He is voiced by Diedrich Bader, who also voices Batman in the same show. His backstory is relatively the same as within the Justice League comics.
After the Crime Syndicate took over their Earth, they decided to use a device known as a Phase Oscillator they stole from Owlman's archenemy, the Red Hood, that could open gateways to other worlds. Once on our world, Owlman was promptly defeated by Batman, who infiltrated the Injustice Syndicate as Owlman.
Somehow escaping, Owlman masqueraded as Batman in his doppelgänger's old costumes and framed the Dark Knight for crimes around Gotham City. This sent many of the Caped Crusader's allies after him, forcing the Batman to work with his top foe, the Joker. On Batman's earth, he gathered Black Manta, the Brain, Gorilla Grodd, Clock King, Gentleman Ghost and Dr. Polaris and captured the heroes. He even turned Joker on Batman. Fortunately in a battle royale, Batman gathered together Batmen from parallel earths and battled Owlman's syndicate, freeing the other heroes. Owlman, alongside the Joker, are defeated and sent to Iron Heights prison and Owlman is sent back to Earth-23 under the intensive care of Justice Underground.