Anna Karenina (Russian: «Анна Каренина», IPA: [ˈanːə kɐˈrʲenʲɪnə]) is a novel by the Russian author Leo Tolstoy, first published in book form in 1878. Widely considered to be one of the greatest works of literature ever written, Tolstoy himself called it his first true novel. It was initially released in serial installments from 1875 to 1877, all but the last part appearing in the periodical The Russian Messenger.

A complex novel in eight parts, with more than a dozen major characters, Anna Karenina is often published in more than 800 pages. It deals with themes of betrayal, faith, family, marriage, Imperial Russian society, desire, and rural vs. city life. The story centers on an extramarital affair between Anna and dashing cavalry officer Count Alexei Kirillovich Vronsky that scandalizes the social circles of Saint Petersburg and forces the young lovers to flee to Italy in a search for happiness, but after they return to Russia, their lives further unravel.

Trains are a motif throughout the novel, with several major plot points taking place either on passenger trains or at stations in Saint Petersburg or elsewhere in Russia. The story takes place against the backdrop of the liberal reforms initiated by Emperor Alexander II of Russia and the rapid societal transformations that followed. The novel has been adapted into various media including theatre, opera, film, television, ballet, figure skating, and radio drama.

The inspiration behind the character of Anna Karenina is widely considered to be a 37-year-old woman named Anna Stepanova, who worked as a housekeeper for one of Tolstoy’s neighbors. She and her husband regularly argued about his flirtations with governesses. Finally, she became so consumed with jealousy that she threw herself under a train but not before sending off a letter addressed to her husband, which reportedly read, “You are my killer; you will be happy with her if murderers can be happy. If you want to see me, you can view my body on the rails of Yasenki.” As the family knew the woman well, Tolstoy personally went to observe the autopsy; his wife wrote to a friend that he “was terribly shaken. He had known Anna Stepanovna as a tall, stout woman, Russian in face and character, a brunette with grey eyes, not beautiful but attractive.” The episode happened in 1872, just a year before Tolstoy first sketched out the character of Anna Karenina, who likewise had gray eyes.