Eldest son of Aerys II, Rhaegar was the Prince of Dragonstone, the heir-apparent to the Iron Throne. As a character who has been deceased since before the beginning of the books, almost all information on Rhaegar comes second-hand, through the thoughts, recollections and tales of other characters.

An intelligent, handsome, brooding and melancholy man, Rhaegar kept his thoughts closely guarded; while all knew of him (Cersei once commented that when the Targaryens came to Casterly Rock, the smallfolk cheered for Lord Tywin Lannister twice as much as for King Aerys, but only half as loudly as for Rhaegar), few knew him, and he had few real friends (Ser Arthur Dayne, Myles Mootan, Richard Lonmouth & Lord Connington were such).

As a child Rhaegar was bookish to a fault; he took no interest in the play of other children until he found and read something that changed him: he decided that he must be a warrior. At seventeen he was knighted and from all reports he grew into a highly skilled and capable fighter, but took little joy in it (Barristan Selmy once remarked that Rhaegar loved his harp more than he loved his lance). He was born on the same day as the Tragedy at Summerhall, and often liked to visit the ruined hall for solitude, disappearing with only his harp for company and emerging weeks later with new compositions of surpassing beauty and melancholy.

He was champion at the tourney at Harrenhal, the only time he ever won a tourney. He shocked those present at the tourney by passing over his wife, the Dornish princess Elia of Dorne, when selecting the Queen of Love and Beauty. Instead, he crowned Lyanna Stark, a noblewoman of the North, by giving her the crown of winter roses. Rhaegar later disappeared with Lyanna, an act that many people, including Lyanna's family and her betrothed Robert Baratheon, viewed as a kidnapping. While the exact nature of their relationship is not currently known, outrage over the act ultimately triggered the War of the Usurper. Rhaegar was killed by Robert during that conflict at the Battle of the Trident.

His wife, Elia Martell, bore him two children, a girl named Rhaenys and an infant son, Aegon. The princess and her two children were murdered by Ser Gregor Clegane and Ser Amory Lorch during the Sack of King's Landing, under Tywin Lannister's orders.

Though Robert vilified Rhaegar throughout A Game of Thrones, most other characters have expressed admiration for him, including Robert's best friend Ned Stark. Ser Barristan Selmy has stated that Rhaegar is still remembered in Westeros with great love. His younger sister Daenerys Targaryen is sometimes compared to him as a compliment. Maester Aemon remembered that Rhaegar believed his child Aegon to be the 'Prince Who Was Promised'.

From "A Song of Ice and Fire" by George R R Martin