The earliest date given for a Viking raid is 787, when, according to the Anglo Saxon Chronicle, a group of men from Norway sailed to Portland, in Dorset. There, they were mistaken as merchants by a royal official, and they murdered him, when he tried to get them to accompany him to the king's manor to pay a trading tax on their goods. The next recorded attack, dated June 8, 793, was on the monastery at Lindisfarne on the east coast of England. For the next 200 years, European history is filled with tales of Vikings and their plundering.

The period of North Germanic expansion, usually taken to last from the earliest recorded raids in the 790s until the Norman Conquest of England in 1066, is commonly called the "Viking Age." The Vikings may be seen as late joiners in the Migrations period, and thus the period links Late Antiquity with the high Middle Ages.

During three centuries, Vikings appeared along the coasts and rivers of Europe, as raiders, but increasingly also as traders, and even as settlers. From 839 there were Varangian mercenaries in Byzantine service (most famously Harald Hardrada, who campaigned in North Africa and Jerusalem in the 1030s).

Important trading ports during the period include Birca, Hedeby, Kaupang, Jorvik, Staraja Ladoga, Novgorod, and Kiev. Generally speaking, the Norwegians expanded to the north and west, the Danes to England, settling in the Danelaw, and the Swedes, (called the Rus) to the east. But the three nations were not yet clearly separated, and still united by the common Old Norse language.

The names of Scandinavian kings are known only for the later part of the Viking Age, and only after the end of the Viking Age did the separate kingdoms acquire a distinct identity as nations, which went hand in hand with the christianization. Viking navigators also opened the road to new lands to the north and to the west, resulting in the colonialization of Shetland, the Faroe Islands, Iceland, Greenland, and even a short expedition to Newfoundland, circa 1000 AD.

Vikings exerted influence throughout the coastal areas of Ireland and Scotland, and conquered and colonised large parts of England (see Danelaw). They travelled up the rivers of France and Spain, and gained control of areas in Russia and along the Baltic coast. Stories tell of raids in the Mediterranean and as far east as the Caspian Sea.

King Harald I of Norway finally was forced to make an expedition to the west to clear the islands and Scottish mainland of the last pirates Vikings. Numbers of them fled to Iceland, but the Norse sagas are rather subjective in their descriptions, and hence the Vikings in those sagas are sometimes characterized as heroes, later shaping the attitude against Vikings during the 18th century Romantic period.