Haakon Sigurdsson (anord.: Hákon Sigurðarson) or Haakon Jarl, Haakon Ladejarl, Hákon jarl hinn ríki, called "the rich" or "the mighty" (c. 935 in Lade; † 995 in Romol, today's Melhus), was de facto regent of Norway from about 971 until his death in 995 as imperial administrator.
Haakon came from the dynasty of Ladejarl and was the son of Sigurd Håkonsson, Jarl of Trøndelag. His mother was Bergljot Toresdotter, a daughter of Tore Ragnvaldsson, Jarl of Möre, and Princess Alof Aaarbod, a daughter of King Harald Fairhair of Norway from his second marriage to Gyda, a daughter of King Eirik of Hördeland.
Hakon Sigurdsson succeeded his father Sigurd Håkonsson as Jarl of Lade after the latter - who was a friend and advisor of King Haakon the Good of Norway - was murdered by King Harald Graufell of Norway and his brothers in 962.
Hakon fought with Harald Graufell for some time until he was forced to flee to Denmark to join Harald Bluetooth, where he allied with him against Harald Graufell.
When Harald Graufell was killed in 971, Haakon Jarl ruled Norway as Harald Bluetooth's vassal. In fact, however, he was an independent ruler. On Harald Bluetooth's behalf, he attacked Götaland and killed its ruler Jarl Ottar.
In the autumn of 974, after a raid by Harald Bluetooth on northern Albingia, he successfully defended the Danewerk against the first onslaught of an imperial army of Saxons, Franks, Frisians and Abodrites led by Emperor Otto II, Saxon Duke Bernhard I and Count Heinrich von Stade.
When Haakon Jarl noticed how the enemy army was preparing to cross the Schlei River with the help of the Abodritic fleet, thus bypassing the Danewerk, he and his followers retreated to Norway.
Haakon Jarl believed in the old gods, and when Harald Bluetooth tried to force him to convert to Christianity around 975, his loyalty to Denmark broke.
In the battle of Hjørungavåg in 986, a Danish invasion army was defeated, after which Denmark lost power over Norway for a short time. In 977, Vladimir of Kiev fled to Haakon Jarl.
He gathered as many Viking warriors as he could to retake Novgorod, on his return the following year he marched against Jaropolk I.
In 995 there was a rift between the Trønders and Haakon Jarl when Olaf Tryggvason appeared in Trøndelag. Haakon Jarl quickly lost all support and had to flee to the Rimol (now Romol) farm in Melhus, where he was murdered by his own slave and friend Tormod Kark.
His two sons Erik and Sven and some others fled to the Swedish king Olof Skötkonung. Haakon Jarl's death was to be avenged in the naval battle of Svold.
Haakon Jarl had a number of skalds in his retinue: Øyvind Skaldespiller, Einar Helgason called Einar Skalaglam, Tindr Hallkelsson, Eilífr Goðrúnarson.