It is a fact that Harald was the youngest of King Olaf II of Norway. Harald was born in 1015 (or maybe 1016) in Ringerike, Norway to Sta Gudbrandsdatter and her second husband Sigurd Syr. Sigurd was a Ringerike minor king and one of the strongest and wealthiest chieftains in the Uplands. Harald was the youngest of King Olaf II of Norway's three half-brothers by his mother sta (Olaf II Haraldsson, later known as Saint Olaf (and traditionally as St. Olave), was King of Norway from 1015 to 1028). Harald was a typical rebel with huge dreams in his childhood, and he looked up to Olaf as a role model. He so contrasted with his two elder brothers, who were more like their father, down-to-earth, and mostly concerned with farm maintenance.

The Icelandic sagas, particularly Snorri Sturluson's Heimskringla, suggest that Sigurd, like Olaf's father, was a male-line great-grandson of King Harald Fairhair. Most current academics believe that the forebears assigned to Harald Hardrada's father, as well as other elements of the Fairhair genealogy, are inventions reflecting the authors' political and social ambitions rather than historical truth. Harald Hardrada's supposed lineage from Harald Fairhair is never stated or played any role during his lifetime, which is odd given that it would have supplied important legitimacy in conjunction with his claim to the Norwegian crown.

One of the interesting facts about Harald Hardrada is that Harald was only fifteen when the battle of Stiklestad took place. Following a revolt in 1028, Harald's brother Olaf was thrown into exile until early 1030, when he returned to Norway. When Harald learned of Olaf's impending return, he assembled 600 soldiers from the Uplands to meet Olaf and his men when they arrived in Norway's east. Following a warm welcome, Olaf proceeded to build an army and eventually engage in the Battle of Stiklestad on July 29, 1030, in which Harald fought on his brother's side. The battle was part of an attempt to restore Olaf to the Norwegian crown, which had been taken by Cnut the Great of Denmark (Canute).

The battle ended in defeat for the brothers at the hands of Cnut's faithful Norwegians, and Olaf was killed while Harald was severely wounded. Despite this, Harald was noted to have displayed tremendous military skill during the conflict.

The Battle of Stiklestad, fought in 1030, is one of Norway's most renowned engagements. King Olaf II of Norway (láfr Haraldsson) was killed in this fight. During Pope Alexander III's pontificate, the Roman Catholic Church made Olaf a saint in 1164. The battle's historical accuracy is being called into question. According to contemporary reports, the king was assassinated. Olaf was assassinated by his own people, according to the Anglo Saxon Chronicle of 1030. Olaf was killed in an ambush, according to Adam of Bremen in 1070, and Florence of Worcester around 1100. These are the only contemporary sources that mention the king's death.

Another interesting fact about Harald Hardrada is that he led the soldiers of Prince Yaroslav of Kievan Rus. Following his defeat at the Battle of Stiklestad, Harald managed to flee to an isolated farm in Eastern Norway with the assistance of Rögnvald Brusason. He stayed for a while to cure his wounds before traveling north through the mountains to Sweden (perhaps up to a month later). Harald came in Kievan Rus a year after the Battle of Stiklestad. He most likely spent some time at the town of Staraya Ladoga (Aldeigjuborg), where he arrived in the first half of 1031. Grand Prince Yaroslav the Wise, whose wife Ingegerd was a distant relative of Harald, greeted Harald and his warriors.

In desperate need of military leaders, Yaroslav recognized Harald's military aptitude and appointed him captain of his soldiers. Olaf Haraldsson, Harald's brother, had previously been in exile in Yaroslav during the insurrection in 1028, and Morkinskinna claims that Yaroslav accepted Harald first and foremost because he was Olaf's brother. Harald participated in Yaroslav's expedition against the Poles in 1031, and may also have fought against other 1030s Kievan opponents and competitors such as the Chudes in Estonia, the Byzantines, the Pechenegs, and other steppe nomad populations.

One of the interesting facts about Harald Hardrada is that Harald was discovered battling on the empire's almost every frontier. After a few years in Kievan Rus', Harald and his force of around 500 men moved on south to Constantinople (Miklagard), the capital of the Eastern Roman Empire (later known as the Byzantine Empire), probably in 1033 or 1034, where they joined the Varangian Guard. Although the Flateyjarbók claims that Harald initially tried to conceal his royal status, most sources agree that Harald and his troops were well known in the east at the time. While the Varangian Guard was intended to be the emperor's bodyguard, Harald was found fighting on "almost every frontier" of the empire.

He initially saw battle in campaigns against Arab pirates in the Mediterranean Sea, and then in towns in Asia Minor/Anatolia that had backed the pirates. By this time, he had risen to the position of leader over all the Varangians, according to Snorri Sturluson. By 1035, the Byzantines had pushed the Arabs out of Asia Minor to the east and southeast, and Harald participated in campaigns that went as far east as the Tigris and Euphrates rivers in Mesopotamia, where, according to his skald (poet) Þjóðólfr Arnórsson (recounted in the sagas), he participated in the capture of eighty Arab strongholds. Although not maintaining independent command of an army as the sagas claim, it is not impossible that King Harald and the Varangians at times could have been sent off to seize a fortress or town. Harald most likely fought in operations against the Pechenegs during the first four years of Byzantine Emperor Michael IV the Paphlagonian's reign.

It is a fact that he married Yaroslav’s daughter Princess Elisaveta (Elisiv). Harald requested permission to return to Norway after Zoe and Constantine IX were restored to the throne in June 1042. Despite Zoe's refusal, Harald managed to escape into the Bosphorus with two ships and a few faithful companions. The Byzantine cross-strait iron chains destroyed the second ship, but Harald's ship sailed safely into the Black Sea after successfully maneuvering over the barrier. Despite this, Kekaumenos praises Harald's commitment and passion for the empire, which he apparently maintained even after returning to Norway and becoming king. Harald returned to Kievan Rus later that year after fleeing Constantinople. During his second visit, he married Elisabeth (known as Ellisif in Scandinavian sources), the daughter of Yaroslav the Wise and granddaughter of Swedish King Olof Skötkonung. Yaroslav attacked Constantinople shortly after Harald arrived in Kiev, and it is thought that Harald provided him with crucial information on the state of the empire.

It's probable that the marriage with Elisiv was already agreed upon during Harald's first visit to Rus', or that they were at least acquainted. During his service in the Byzantine Empire, Harald wrote a love poem in which he said that she would not accept his gold rings, though Morkinskinna claims that Harald had to remind Yaroslav of the promised marriage when he returned to Kiev. According to the same story, Harald approached Yaroslav during his first visit to Rus', wanting to marry Elisiv, but was turned down since he was not wealthy enough. In any event, the fact that Harald was permitted to marry Yaroslav's daughter is important, given that his other children were married to individuals such as Henry I of France, Andrew I of Hungary, and the daughter of Constantine IX.

One of the interesting facts about Harald Hardrada is that he and Magnus became the joint ruler of Norway in 1046. Seeking to regain the kingdom lost by his half-brother Olaf Haraldsson, Harald set out in early 1045 from Novgorod (Holmgard) towards Staraya Ladoga (Aldeigjuborg), where he obtained a ship. His trek took him through Lake Ladoga, the Neva River, the Gulf of Finland, and the Baltic Sea. He landed in Sigtuna, Sweden, around the end of 1045 or the beginning of 1046. According to the skald Tjodolv Arnorsson, when he landed in Sweden, his ship was unstable due to its heavy load of gold. In Harald's absence, Norway's throne had been restored to Magnus the Good, Olaf's illegitimate son. Harald may have been aware of this, and it is possible that this is why Harald desired to return to Norway in the first place. Magnus's position as the king had been assured since Cnut the Great's sons had decided to flee Norway and fight over England, and his sons and successors Harold Harefoot and Harthacnut had died young. During his eleven-year reign, no domestic threats or insurrections were documented. After Harthacnut's death, which left the Danish throne vacant, Magnus was also chosen to be King of Denmark, and he defeated the Danish royal pretender Sweyn Estridsson.

When Harald learned of Sweyn's defeat at the hands of Magnus, he joined forces with his fellow exile in Sweden (who was also his nephew), as well as the Swedish king Anund Jacob, and the three joined forces against Magnus. Their first military adventure was a raid on the Danish shore. The goal was to impress the people by demonstrating that Magnus provided little protection, prompting them to submit to Harald and Sweyn. Magnus deduced from their behavior that their next target would be Norway. Harald may have intended to be crowned king of his father's minor realm before claiming the rest of the country. In any case, the people were unwilling to rally against Magnus, and upon learning of Harald's plans, Magnus returned to Norway with his entire army. Instead of fighting his uncle, Magnus' counselors advised him not to, and a solution was negotiated in 1046 in which Harald would rule Norway jointly with Magnus. Notably, Harald was also forced to agree to share half of his riches with Magnus, who was essentially bankrupt and in desperate need of finances at the time. Harald and Magnus held separate courts and stayed to themselves during their brief co-rule, and their sole known interactions nearly ended in physical fights.

It is a fact that Harald Hardrada died at the Battle of Stamford Bridge. Harald and Tostig departed Riccall with the majority of their men early on September 25th but left one-third of their soldiers behind. They packed just light armor since they intended to meet the citizens of York at Stamford Bridge the day before to decide who would manage the town under Harald. Harald noticed Godwinson's forces approaching, fully armed and armored, and far outnumbering Harald's. Despite the fact that the English forces were held up at the bridge for some time by a single massive Norwegian, allowing Harald and Tostig to reassemble into a shield-wall configuration, Harald's army was heavily crushed in the end. Harald was killed in a condition of berserkergang, having worn no body armor, and fought furiously with both hands around his sword, early in the conflict, afterward dubbed the Battle of Stamford Bridge.

When the battle was nearly ended, some Riccall reserve forces led by Eystein Orre emerged, but they were fatigued from running all the way. Eystein took up Harald's fallen banner, the "Landwaster", and launched a final counter-attack. Although they appeared to be on the verge of breaching the English line, Eystein was abruptly murdered, forcing the rest of the troops to escape the battlefield. Harald's son Olaf was among that left at Riccall after the battle and allowed to return home peacefully by the English army. Although records claim that Harald's surviving army only filled 20-25 ships on the trip back to Norway, this figure most likely only includes Norwegian forces. The majority of the men from Scotland and Orkney were most likely stationed at Riccall during the fight and are not included in the standard number.

Harold Godwinson's success was short-lived, as he was defeated and slain at the Battle of Hastings by William the Conqueror only a few weeks later. Harold's forced march to combat Hardrada at Stamford Bridge and then advance at breakneck speed south to confront the Norman invasion, all in less than three weeks, is largely regarded as a major element in William's triumph at Hastings.