Romerike is a traditional district located north-east of Oslo, in what is today south-eastern Norway. It consists of the Akershus municipalities Fet, Lørenskog, Nittedal, Rælingen, Skedsmo, Sørum and Aurskog-Høland in the southern end (Nedre Romerike), and Ullensaker, Gjerdrum, Nannestad, Nes, Eidsvoll and Hurdal in the northern end (Øvre Romerike). 
The Old Norse form of the name was Raumaríki, but the name must be much older (see below). The first element is the genitive plural of raumr m ("person from Romerike"); the final element is ríki n ("kingdom, reich"; cf. Ringerike, Rånrike).
In the Hversu Noregr byggdist and in Thorsteins saga Víkingssonar, the name is attributed to the mythical king Raum the Old (Raumr inn gamli). According to the latter saga, the members of the family were big and ugly, and because of this big and ugly people were called "great Raumar".
Before the Unification of Norway by King Harald Fairhair, Romerike was a petty kingdom. It had its age of greatness between the 5th and 7th centuries. The 6th-century Goth scholar Jordanes wrote in his Getica about a tribe located in Scandza which he named the Raumarici and which seems to be the same name as Raumariki, the old name for Romerike.
In the 9th century, Halfdan the Black, the father of King Harald Fairhair, subdued the area by defeating and killing the previous ruler Sigtryg in battle. He then defeated Sigtryg's brother and successor Eystein in a series of battles.
After the death of Halfdan the Black, it submitted to the Swedish king Erik Eymundsson. However, it was forcibly conquered by Harald Fairhair who had to spend a summer to lead it into the fold of his newly created kingdom of Norway.
The centre of the kingdom was Sand between Jessheim and Garder, where the earliest settlements were situated and where the soil was easy to cultivate. In the surrounding forests there was rich game. Its name may be derived from the Raum elfr an old name for the Glomma river.
Rakni's Mound (Raknehaugen) has been estimated to date to around 550 AD (possibly 552 AD). It is located in the very heart of Romerike. Raknehaugen is a burial mound (gravhaug) from the Old Norse word haugr meaning barrow or mound. It is assumed that it is named after a king with the name Rakni. At 77 metres in diameter and more than 15 metres high, Raknehaugen at Ullensaker is the largest barrow in Northern Europe.