Ragnar Lodbrok(Old Norse Ragnarr Loðbrók, also anglicized as Ragnar Lodbrok), whose epithet means 'Hairy-breeches' or 'Shaggy-breeches', was a legendary Viking king, with Old Norse sagas, poetry, and medieval Latin sources telling of his accomplishments in Scandinavia, Francia, and Anglo-Saxon England during the 9th century CE. Commonly occurring elements in these stories are his marriages to Thora and Aslaug, as well as his fathering of many famous sons including Ivar the boneless, Bjorn Ironside Sigurd Snake-in-the-Eye, Hvitserk, and Ubba. A possible third wife, Lagether, only appears in the 13th-century CE Gesta Danorum, a work on Danish history, as does a fourth, Swanloga.

Perhaps the most iconic titbits of his legend are Ragnar's successful fight with a dragon – for which he fashioned his defining shaggy breeches as protection – and his slightly overconfident invasion of England with just two ships, which ended with him being captured by King Ælla of Northumbria (r. c. 866 CE), who had him killed by throwing him into a snake-pit. Whereas Ragnar's own historicity is highly disputed, some of his alleged sons are often thought to have some basis in actual historical figures.