Deryni Rising is a historical fantasy novel by American-born author Katherine Kurtz.  It was first published by Ballantine Books as the nineteenth volume of the Ballantine Adult Fantasy series in August 1970, and was reprinted at least ten times over the next three decades.  In 2004, the author released a revised and updated edition of the novel that was published by Ace Books.  Deryni Rising was the first of Kurtz' Deryni novels to be published, though some of her later works served as prequels, detailing events that occurred before the time period of Deryni Rising.  As a result, the storyline of the Childe Morgan Trilogy immediately precedes Deryni Rising, despite the fact that it was published over thirty years after the first novel.
 The novel is set in the land of Gwynedd, one of the fictional Eleven Kingdoms.  Gwynedd itself is a medieval kingdom similar to the British Isles of the 12th century, with a powerful Holy Church (based on the Roman Catholic Church), and a feudal government ruled by a hereditary monarchy.  The population of Gwynedd includes both humans and Deryni, a race of people with inherent psychic and magical abilities who have been shunned and persecuted for centuries.  The book takes place almost entirely within Gwynedd's capital city of Rhemuth, and deals primarily with the struggle of young Prince Kelson Haldane to secure his throne from the machinations of a Deryni usurper.
 The book covers a two-week period in November 1120, beginning with the death of King Brion Haldane while leading a hunting party outside the city of Rhemuth.  Immediately following Brion's death, his son and heir, Prince Kelson sends for his father's closest friend and advisor, Alaric Morgan, the Deryni Duke of Corwyn.  Morgan arrives shortly before Kelson's coronation, but his efforts to assist the prince are interrupted by Kelson's mother, Queen Jehana.  However, Kelson manages to thwart Jehana's attempts to imprison Morgan, and the duke resumes his efforts to protect Kelson.
 Morgan informs Kelson that Brion had wielded magical powers of his own, despite the fact that Brion was not Deryni.  Known as "the Haldane potential", it is a trait of the Haldane line to acquire Deryni-like powers once they have been activated in the subject.  Morgan believes that Brion designed a magical ritual to awaken those powers in Kelson.  Furthermore, Morgan suspects that Kelson will need those powers to defend himself from Princess Charissa Furstána-Festila, a Deryni sorceress who intends to attack Kelson during his coronation and claim the throne of Gwynedd.
 During the course of the night, Morgan and his cousin, Monsignor Duncan McLain, attempt to decipher the clues left by Brion.  After a bloody encounter in the royal crypt, the cousins discover that they both possess the Deryni talent for Healing, an ability that has been lost for two centuries.  They eventually attempt to activate Kelson's magical abilities, but are disappointed when the ritual appears to fail.  Later that night, Morgan encounters Charissa in the palace and the sorceress proudly admits to murdering Brion.
 During Kelson's coronation the following morning, Charissa appears and challenges the prince to a Duel Arcane, an ancient form of magical combat.  Morgan attempts to answer the challenge in his role as King's Champion, but Charissa's own champion seriously wounds the Deryni duke before being defeated, leaving Morgan unable to deal with Charissa herself.  However, seeing her son's danger, Jehana attacks Charissa with magic, revealing that her fanatical hatred of Deryni has concealed her own Deryni heritage.  Nonetheless, Charissa easily defeats Jehana, and Kelson is forced to personally duel with the sorceress.  As the combat is about to begin, Kelson suddenly unravels the last of his father's clues and activates his own powers.  Using both his Haldane powers and his newly discovered Deryni heritage, Kelson manages to defeat Charissa.  With the Pretender now dead, Kelson is crowned as King of Gwynedd.
 Deryni Rising was a finalist for the 1971 Mythopoeic Fantasy Award for outstanding work in the field of fantasy literature.  The other finalists were Lloyd Alexander's The Marvelous Misadventures of Sebastian and Roger Zelazny's Nine Princes in Amber.  However, the award was won by Mary Stewart for her novel, The Crystal Cave.
 In 1971, Deryni Rising ranked 12th in an annual poll of Locus magazine readers, placing it between Dean Koontz's Beastchild and D. G. Compton's Chronocules.  (The poll was won by Larry Niven's Ringworld.)  In a 1987 poll, the readers of Locus ranked Deryni Rising as the 29th greatest fantasy novel of all time, placing it in a tie with E. R. Eddison's The Worm Ouroboros.  In 1998, Locus conducted a survey to determine the greatest fantasy novels published before 1990, and Deryni Rising was ranked 30th by the magazine's readers.  Both the 1987 poll and the 1998 poll were won by J. R. R. Tolkien's The Lord of the Rings.