Ragnar Lodbrok, a legendary Norse ruler and hero from the Viking Age and main character in the 2013 TV series "Vikings"
Ragnar Danneskjold, character in AynRand's "Atlas Shrugged"
In Norse mythology, Ragnarök is a series of future events.
Ragnarok, freeware roguelike video game for DOS
Ragnar the Red, a song from the video game "Skyrim"