The Battle of Stiklestad (Norwegian: Slaget på Stiklestad; Old Norse: Stiklastaðaorrusta) in 1030 is one of the most famous battles in the history of Norway. In this battle, King Olaf II of Norway was killed. During the pontificate of Pope Alexander III, the Roman Catholic Church declared Olaf a saint in 1164.

His younger half-brother, Harald Hardrada, was also present at the battle. Harald was only fifteen when the battle of Stiklestad took place. He became King of Norway in 1047, until his death in a failed invasion of England at the Battle of Stamford Bridge in 1066.

During the 9th century, Norway was divided among several local kings controlling their own fiefs. By the end of the century, King Harald Fairhair managed, mainly due to the military superiority gained by his marriage alliance with Hákon Grjótgarðsson of Nidaros, to subjugate these mini–kingdoms, and he created a unified Norwegian state.

This alliance came apart after Harald's death. The jarls of Lade and various descendants of Harald Fairhair would spend the next century interlocked in feuds over power. As well as power politics, religion also played a part in these conflicts, as two of the descendants of Harald Fairhair, Haakon the Good and Olaf Tryggvason attempted to convert the then heathen Norwegians to Christianity. In the year 1000, Sveinn Hákonarson and Eiríkr Hákonarson of Lade took control over Norway, being supported by the Danish King Sweyn Forkbeard. In 1015, Olaf Haraldsson, representing the descendants of Harald Fairhair, returned from one of his Viking trips and was immediately elected as King of Norway. In June 1016, he won the Battle of Nesjar against the jarls of Lade.

Olav Haraldsson's success in becoming King of Norway was helped by the Danes being kept occupied with the ongoing fighting in England. In the year 1028, the Danish king Cnut the Great made an alliance with the Lades, and Olaf had to go into exile in Kievan Rus'. In the year of 1029 the last Lade jarl, Haakon Ericsson, drowned, and Olaf prepared a military expedition to reclaim the throne. Olaf was supported by the Swedish king Anund Jacob who wanted to weaken Cnut's power and provided Olaf with 400 men and guides that could lead Olaf through Dalarna into Norway. Dagr Hringsson, a Norwegian noble in exile in Sweden and governor for Anund Jacob also joined forces with Olaf on the condition that his old lands would be restored to him. On route, Olaf also recruited several highwaymen before mustering for forces in Jämtland.

According to saga sources, Olaf traveled with his 3,600 man army through Sweden and crossed the mountains into the valley of Verdalen, about 80 kilometres (50 mi) north of the city of Trondheim. Olaf and his men arrived at Stiklestad, a farm in the lower part of the valley. This was where the Battle of Stiklestad took place, as described by Snorri Sturluson in his famous work Heimskringla, written about 200 years later.

At Stiklestad, Olaf met an army led by Hárek of Tjøtta, Thorir Hund from Bjarkøy and Kálfr Árnason, a man who previously served Olaf. The farmer army consisted of one hundred hundred according to Snorri, which in long hundreds means 14,400, and not 10,000. He states that the battle cry of Olaf's men was Fram, fram, kristsmenn, krossmenn, konungsmenn! (Forward! Forward! Men of Christ, men of the cross, men of the king!), while that of the opposing army was Fram, fram, búandmenn! (Forward! Forward! Farmers!). Olaf's brother Harald was according to some sources instructed to remain in the camp, but convinced his older brother to let him fight.

According to Snorri, Olaf received three severe wounds – in the knee, in the neck, and while leaning against a large stone the final mortal spear thrust up under his mail shirt and into his belly. According to saga sources, Thorir was among those who gave Olaf his lethal wounds, together with Kálfr Árnason and Torstein Knarresmed from Rovde in Sunnmøre. While earlier sources do not specify who dealt the king his blows, Snorri makes Thorir Hund responsible for the latter, using the spear that had killed his nephew and set the fallout between the king and Thorir in motion. Bjørn Stallare, the king's marshall, almost killed Thorir with a "axe-hammer" (a type of early warhammer). However, Torstein Knarresmed managed to get between them and gave Olaf a wound right above his left knee. Thorir Hund stabbed Bjørn to death with his spear and shortly later thrust his spear into the king's stomach. Kálfr Árnason then struck the king in the throat with his sword. Torstein Knarresmed was subsequently killed by a blow in the back but was revenged later that same day by one of Thorir's men. Dagr Hringsson continued to fight after the king's death but as the king's flank was scattered Kalv and Thorir set their attention to Dagr, forming a wedge formation which forced Dagr and the remainder of Olaf's army retreat. Harald was wounded in the battle and fled after the king's death, being taken in and hidden by locals on account of his youth and not knowing that he was Olaf's brother. The king's body was carried away and buried secretly in the sandy banks of the Nidelva River south of the city of Trondheim.