Lloyd Chudley Alexander (January 30, 1924 – May 17, 2007) was an American author of more than 40 books, primarily fantasy novels for children and young adults. Over his seven-decade career, Alexander wrote 48 books, and his work has been translated into 20 languages. His most famous work is The Chronicles of Prydain, a series of five high fantasy novels whose conclusion, The High King, was awarded the 1969 Newbery Medal for excellence in American children's literature. He won U.S. National Book Awards in 1971 and 1982.

Alexander grew up in Pennsylvania during the Great Depression. He developed a passion for reading books and writing poetry. He attended college for only one term, believing that there was nothing more college could teach him. He enlisted in the United States Army and rose to be a staff sergeant in intelligence and counter-intelligence. He met his wife while he was stationed in France and studied French literature at the University of Paris. After returning to the United States with his new family, he struggled to make a living from writing until he published And Let the Credit Go (1955), his first autobiographical novel. His interest in Welsh mythology led to the publication of The Chronicles of Prydain.

Alexander was nominated twice for the international Hans Christian Andersen Award, and received the 1971 National Book Award for Children's Books for The Marvelous Misadventures of Sebastian and the 1982 National Book Award for Westmark. Alexander received three lifetime achievement awards before his death in 2007. The Harold B. Lee Library at Brigham Young University contains a permanent Lloyd Alexander exhibit that showcases several items from his home office including his desk, typewriter, and manuscripts and editions of his books.

Alexander was born in Philadelphia on January 30, 1924, to Edna (née Chudley) and Alan Audley Alexander, and grew up in Drexel Hill, Pennsylvania, a section of Upper Darby, just west of the city. He had an elder sister, Florence. His parents only read newspapers, but they did buy books "at the Salvation Army to fill up empty shelves". He taught himself to read around age four and skipped grades one and two at a private Quaker school. He and his friends played war, using equipment from World War I in their games. After his father Alan, a stockbroker, bankrupted in the Wall Street Crash of 1929, Alexander attended public school, where he skipped yet another grade, entering seventh grade at age nine. Alexander read Shakespeare, Dickens, Mark Twain and myths, especially King Arthur. In addition to being interested in art, at age thirteen, Alexander wanted to become an Episcopal priest; however, his family could not afford to send him to divinity school. Passionate about writing, Alexander believed he could preach and worship God through his writing and his art. In high school, he began writing romantic poetry modeled after the work of nineteenth-century poets and narrative short stories, but he failed to acquire interest from publishers. His parents found him a job as a bank messenger, which inspired a satire that would become his first book published fifteen years later, And Let the Credit Go (1955). He graduated at age sixteen in 1940 from Upper Darby High School, where he was inducted into the school's Wall of Fame in 1995.

He attended West Chester State Teachers College, which he left after only one term because he did not find the curriculum rigorous enough. After dropping out of college, Alexander worked for six months in the mailroom of the Atlantic Refining Company. Alexander decided that adventure was a better school for a writer than college and enlisted in the U.S. Army during World War II. He was too clumsy with artillery to be sent to the front, and the sight of blood made him faint, making him unfit to work as a medic. With no prior musical experience, he briefly played the cymbals in a marching band in Texas. Shortly after, he was transferred to serve as a chaplain's assistant. He had the opportunity to study the French language, politics, customs, and geography at Lafayette College through the army. He was later moved to Camp Ritchie, Maryland, to receive specialized intelligence training in the United States Army Combat Intelligence and Counter-Intelligence Corps. At Camp Ritchie, Alexander rose to the rank of Staff Sergeant. There he met war veterans, scholars, refugees, and members of the Cherokee tribe. He rose to be a staff sergeant in the corps.

Alexander was stationed in Wales and England briefly and then was assigned to the 7th Army in eastern France where he translated radio messages for six months. His next assignment was the Paris office of the Counter Intelligence Corps (CIC) where he worked as a translator and an interpreter until the end of 1945. After the war, Alexander attended the University of Paris where he studied French literature and was fascinated by the poetry of Paul Éluard. Alexander called Éluard on the phone and showed him his English translations of Éluard's work. Éluard immediately named Alexander his sole English translator. Alexander also contacted Gertrude Stein, who advised him that becoming a writer was a difficult and discouraging process. In Paris, he met Janine Denni, who had a young daughter named Madeleine. Alexander and Denni were married on January 8, 1946, and soon moved to Philadelphia. The three moved into the attic of his parents' home where Alexander spent twelve hours a day translating Éluard's works and writing his own.

For about fifteen years in Philadelphia, Alexander wrote primarily fiction, non-fiction, and translations for adults. Desperate for a job, he worked as a potter's apprentice for his sister. At the end of 1948, he started writing advertising copy, and he began to receive more royalties for his translations, leading him to purchase a house for his family in Kellytown. However, he lost his job after three months, requiring his wife to take up employment in a textile mill to make ends meet. Alexander continued to write diligently, though no publishers bought his novels for seven years.

One of his short stories, "The Fantastic Symphony" (1949), published in the New Directions Annual, was a surrealistic piece inspired by Berlioz's notes on the Symphonie fantastique. Alexander's breakthrough came with his novel And Let the Credit Go (1955), his first autobiographical work, in which he focused on his experience as a bank messenger in his adolescence. He wrote his second novel, My Five Tigers (1956), about his cats, continuing the trend of writing about subjects familiar to him. He found work as a copyeditor and a cartoonist where he finished his last four adult publications. He wrote two semi-autobiographical novels: Janine is French (1959) and My Love Affair with Music (1960). Alexander co-authored Park Avenue Vet (1960) with Louis Camuti, who specialized in treating cats. The American Society for the Prevention of Cruelty to Animals subsequently commissioned their history, which Alexander wrote as Fifty Years in the Doghouse (1964). During that time he wrote two non-fiction books for children, biographies for August Bondi and Aaron Lopez commissioned by the Jewish Publication Society, the former of which won the National Jewish Book Award in 1959. Alexander's subsequent novel was his first of the fantasy genre: Time Cat (1963). He later called it "the most creative and liberating experience of my life". The novel imagines a cat who can visit its other lives in different time periods, which Alexander researched extensively. Fifty Years in the Doghouse (1964; reprinted as Send for Ryan) told stories of how William Michael Ryan saved animals as part of his job as a special agent for the ASPCA.