Hamar [ˈhɑ̂ːmɑr] ^ⓘ is a town in Hamar Municipality in Innlandet county, Norway. Hamar is the administrative centre of Hamar Municipality. It is located in the traditional region of Hedmarken. The town is located on the shores of Mjøsa, Norway's largest lake. Historically, it was the principal city of the former Hedmark county, now part of the larger Innlandet county.

The town of Hamar lies in the southwestern part of Hamar Municipality. The 14.21-square-kilometre (5.49 sq mi) town has a population (2024) of 30,030 and a population density of 2,113 inhabitants per square kilometre (5,470/sq mi). The urban area of the town actually extends over the municipal borders into both Ringsaker Municipality and Stange Municipality. About 1.7 square kilometres (420 acres) and 2,438 residents within the town are actually located in Ringsaker Municipality and another 0.3 square kilometres (74 acres) and 332 residents of the town are located within Stange Municipality.

The municipality (originally the town) is named after the old Hamar farm (Old Norse: Hamarr). The medieval market was first built on this farm, and that market eventually became a kjøpstad which in turn became a self-governing municipality. The name is identical with the word hamarr which means "rocky hill".

The coat of arms was granted on 2 June 1896. The arms show a Black Grouse sitting in the top of a pine tree on a white background. An older version of the arms had been used for a long time. The old version was first described in the anonymous Hamar Chronicle, written in 1553.

Between 500 and 1000 AD, the Åker farm was one of the most important power centres in Norway, located just a few kilometres away from today's town of Hamar. Three coins found in Ringerike in 1895 have been dated to the time of Harald Hardråde and are inscribed Olafr a Hamri.

At some point, presumably after 1030 but clearly before 1152, the centre was moved from Åker to the peninsula near Rosenlundvika (today Domkirkeodden) in what is now the town of Hamar. There are some indications that Harald Hardråde initiated this move because he had property at the new site.

Much of the information about medieval Hamar is derived from the Hamar Chronicle, dated to about 1550. The town is said to have reached its apex in the early 14th century, dominated by the Hamar Cathedral, the bishop's manor, and a fortress, plus the surrounding urbanization. The town was known for its fragrant apple orchards, but there were also merchants, craftsmen, and fishermen in the town.

After the Christianization of Norway in 1030, Hamar began to gain influence as a centre for trade and religion. In 1152, the episcopal representative Nikolaus Breakspear founded Hamar Kaupangen as one of five dioceses in medieval Norway. This diocese included all of Hedemarkens Amt and Christians Amt, which were both separated from the Diocese of Oslo in 1152. The first bishop of Hamar was Arnold, Bishop of Gardar, Greenland (1124–1152). He began to build the (now ruined) Cathedral of Christ Church, which was completed about the time of Bishop Paul (1232–1252). Bishop Thorfinn (1278–1282) was exiled and died at Ter Doest abbey in Flanders, and was later canonised. Bishop Jörund (1285–1286) was transferred to Trondheim. A provincial council was held in 1380. Hamar remained an important religious and political centre in Norway, organized around the cathedral and the bishop's manor until the Reformation that took place in 1536–1537. At this time, Hamar lost its status as the seat of the Diocese after the last Catholic bishop, Mogens Lauritssøn (1513–1537), was taken prisoner in his castle at Hamar by Truid Ulfstand, a Danish noble, and then sent to Antvorskov in Denmark, where he was mildly treated until he died in 1542. At Hamar's peak, there was a Cathedral chapter with ten canons, a school, a Dominican Priory of St. Olaf, and a monastery of the Canons Regular of St. Anthony of Vienna.