The Battle at Herdaler was a battle between the Norse Viking leader Olav Haraldsson (later King Olaf II of Norway, also Saint Olaf) and local Finnish people at Herdaler in Finland around years 1007/8. The Saga of Olaf Haraldson tells how Olav raided the coasts of Finland and was almost killed in the battle.
<blockquote> After this they sailed to Finland and plundered there, and went<br> up the country. All the people fled to the forest, and they had<br> emptied their houses of all household goods. The king went far<br> up the country, and through some woods, and came to some<br> dwellings in a valley called Herdaler, -- where, however, they<br> made but small booty, and saw no people; and as it was getting<br> late in the day, the king turned back to his ships. Now when<br> they came into the woods again people rushed upon them from all<br> quarters, and made a severe attack. The king told his men to<br> cover themselves with their shields, but before they got out of<br> the woods he lost many people, and many were wounded; but at<br> last, late in the evening, he got to the ships. The Finlanders<br> conjured up in the night, by their witchcraft, a dreadful storm<br> and bad weather on the sea; but the king ordered the anchors to<br> be weighed and sail hoisted, and beat off all night to the<br> outside of the land. The king's luck prevailed more than the<br> Finlanders' witchcraft; for he had the luck to beat round the<br> Balagard's side in the night. and so got out to sea. But the<br> Finnish army proceeded on land, making the same progress as the<br> king made with his ships. So says Sigvat: --<br><br>
"The third fight was at Herdaler, where<br> The men of Finland met in war<br> The hero of the royal race,<br> With ringing sword-blades face to face.<br> Off Balagard's shore the waves<br> Ran hollow; but the sea-king saves<br> His hard-pressed ship, and gains the lee<br> Of the east coast through the wild sea."<br> </blockquote>
The location of "Herdaler" in Finland is not certain. The expedition's possible place could have been in Uusimaa in Hirdal in the present-day town of Inkoo. That makes it the first mentioning of a place located in present-day Finland in historical literature.