Ra's al Ghul, sometimes written Rā's al Ghūl, is a DC Comics supervillain and an enemy of Batman. His name is Arabic for "the ghoul's head" (the Demon's Head, see Algol). Created by writer Dennis O'Neil and artist Neal Adams, he was introduced in Batman #232's "Daughter of the Demon" (June 1971). He has also come into conflict with Superman and other DC Comics superheroes. Little is known of the early years of the nearly immortal Ra's, but it is accepted that he has lived for many centuries due to the Lazarus Pits' mysterious brews that restore his youth. A brilliant master of strategy and organization, Ra's al Ghul's goal is to save the earth from ecological devastation by destroying most of its population. He recognizes Batman as both a worthy foe and a possible ally--except that Batman cannot accept his dystopic worldview. Batman also shares a love-hate relationship with Ra's daughter, the beautiful Talia. Ra's also commands a legion of followers dedicated to bringing his version of an earthly paradise to fruition.

Ra's al Ghul is an international terrorist and assassin whose ultimate goal is a world in perfect environmental balance. He believes that the best way to achieve this balance is to eliminate most of humanity. Ra's usually tries to assault the world's human populace with a biological weapon, such as a genetically-engineered virus. He is aided in this quest by the Lazarus Pits, reservoirs of rejuvenating chemicals that restore the dying to life; these pits have granted him a lifespan of several hundred years.

He considers Batman his worthiest opponent, and has frequently sought to make the Dark Knight his successor. He is one of the few criminals in Batman's rogues gallery to have deduced his secret identity as Bruce Wayne. Ra's usually refers to Batman as 'Detective', possibly in recognition of his formidable mental prowess, and the intellectual battles in which they engage, as opposed to Batman's traditional physical conflict. For his own part, Batman's opposition to Ra's is complicated by his love for the villain's daughter, Talia.

Ra's is set free by the son of a dying elderly woman, whom Ra's had earlier examined. The son feels that he owes Ra's a debt for easing his mother's suffering during her last few hours. Ra's and the son head into the desert to seek the tribe of Ra's birth. Ra's convinces the head of his tribe, his uncle, to follow Ra's in his quest for revenge by promising the downfall of the king of the city. By understanding the germ theory of disease hundreds of years before anyone else, Ra's is able to infect the prince with a deadly virus by sending him contaminated fabrics. When the ruler of the city comes to ask Ra's to cure the prince again, Ra's kills both him and his son. Ra's then leads his tribe to raze the city to the ground and kill all of its inhabitants. Subsequently, Ra's declares himself the "Demon's Head."

Ra's spends the next several centuries journeying the world. He fights in the Napoleonic Wars and the French Revolution and becomes a formidable warrior. During this time, Ra's, his uncle, and the boy are all using the Lazarus Pits to prolong their lives until an incident in London. Ra's catches the boy writing his own memoirs in their original language, of which Ra's has forbidden all records. During a battle, Ra's kills the boy and flees to a Lazarus Pit, which he uses. When he returns to their home in London, his uncle has vanished with the remnants of their historical records.