He was probably born in modern Norway, and later became part of the ruling class in Denmark. At some point, he became king there, and later gained control of Sweden and Finland (then a part of Sweden), as well. He was given the nickname "hairy breeches" because he favored trousers made from animal skin by his wife.
He spent most of his life as a pirate and raider, invading one country after another. He would generally accept a huge payment to leave his victims alone, only to come back later and demand more riches in exchange for leaving. But as the extent of his realm shows, he was also a gifted military leader.
By 845, he was a powerful ruler, and most likely a contemporary of the first ruler of Russia, the Viking Rurik. It is said he was always seeking new adventures because he was worried that his freebooting sons would do things that outshined his own achievements.
In that year, he sailed southward, looking for new worlds to conquer. With 120 ships and 5,000 Viking warriors, he landed in modern France, probably at the Seine estuary, and ravaged West Francia, as the westernmost part of the Frankish empire was then known.
Also in 845, Paris was captured and held ransom by a Viking raider, whom the sagas say was Ragnar Lodbrok. The traditional date for this is March 28, which is today referred to as Ragnar Lodbrok Day by many Scandinavians. The King of West Francia, Charlemagne’s son Charles II "The Bald", paid him a fantastic amount of money not to destroy the city. Ragnar Lodbrok, according to Viking sources, was satisfied with no less than 7,000 pounds of silver in exchange for sparing the city. However, that did not stop Ragnar from attacking other parts of France, and it took a long time for the Franks to drive him out.
Ragnar was a pagan who claimed to be a direct descendant of the god Odin. One of his favorite strategies was to attack Christian cities on holy feast days, knowing that many soldiers would be in church.
After he was done with France, he turned his attention to England. In 865, he landed in Northumbria on the northeast coast of England. Here, it is claimed that he was defeated in battle for the only time, by King Ella of Northumbria. Ella’s men captured Ragnar, and the King ordered him thrown into a snake pit filled with poisonous snakes. As he was slowly being bitten to death, he was alleged to have exclaimed "How the little pigs would grunt if they knew the situation of the old boar!"
One Viking saga states that when his four sons heard the manner of his death, they all reacted in great sorrow. Hvitserk, who was playing chess, gripped the piece so hard that he bled from his fingernails. Bjorn grabbed a spear so tightly that he left an impression in it, and Sigurd, who was trimming his nails, cut straight through to the bone.
Ragnar’s fourth son, Ivor “the Boneless”, soon learned the details of his father’s death and swore that he would avenge his father’s death and subsequent killing, in time-honored Viking tradition. In 866, Ivor crossed the North Sea with a large army, met King Ella in battle, and captured him. He sentenced him to die according to the custom of the “blood red eagle”, which was to cut the ribs of the victim out and the lungs removed by grasping them and spreading them over the body. He then avenged his father’s death in exactly this manner.
Although this story, like virtually all tales concerning Ragnar Lodbrok, may or may not be accurate, his death had serious consequences. Ivor was the mastermind behind the attacks on the English mainland in the final quarter of the ninth century. He invaded East Anglia, and the following year attacked York. He was aided by the internal struggle for power in Northumbria--which he was of course responsible for by killing Ella. These wars were a prelude to the long struggle of the Saxons of Alfred the Great against the "Danes" a generation later.
Meanwhile, in France, the Vikings kept coming back for more booty. Among their feats was destroying the city of Rouen several times. Ultimately, many of them settled there permanently, in a land that became known as Normandy (for "Northmen", as the Franks called the Vikings).