Kristiansund was established as a municipality 1 January 1838 (see formannskapsdistrikt). The island and municipality of Grip was merged with Kristiansund 1 January 1964. The island and municipality of Frei was merged with Kristiansund 1 January 2008.
The city, formerly named "Christiansund", is named after the Danish-Norwegian king Christian VI in 1742. The last element of the name, sund, means 'strait, sound'. The old name of the town/village (originally the island Kirkelandet) was Fosna or Fosen — from Old Norse fólgsn f 'hiding place' (here 'hidden port'). It was also often named Lille Fosen ('the small Fosen') to distinguish it from the island Storfosen ('the big Fosen') in Ørland.
Until 1877 the name was written Christianssund, in the period 1877-1888 Kristianssund, from 1889 on Kristiansund.
Before the introduction of postal codes in Norway in 1968 it was easy to confuse the name Kristiansund with Kristiansand in the south. It was therefore obligatory to always add an N (for north) to Kristiansund (Kristiansund N), and an S (for south) to Kristiansand (Kristiansand S).
Another myth concerning the coat of arms is that there was a mix up, between Kristiansund's and Molde's intended shield. The Dano-Norwegian government officials in charge of the giving of the coats, had a party to remember the momentous occasion and became too drunk and hungover to remember which was which, and so Molde got the coat with a whale (which are scarce in between the Romsdal fjords) and Kristiansund got the waterfall (Since Molde is on the mainland and Kristiansund lies in the open sea, it would be more likely that the waterfall was intended for Molde's mountains and the whales for Kristiansund.)
Kristiansund is built on five islands, where Nordlandet ("North Land"), humorously called Marokko ("Morocco"), is the largest, and the site of the local airport, Kvernberget (IATA code: KSU). Gomalandet and Kirk(e)landet ("Church Land"), second and third in size, are considered separate "lands" (islands) even though they are connected. The smallest island is Innlandet ("Innermost Land"; humorously, "Tahiti"). It also consists of the island of Frei which was, until 1 January 2008, not a part of Kristiansund. Frei has now merged into Kristiansund municipality.
Frei is now the largest of the five islands of Kristiansund, even though there are many more smaller islands in Kristiansund, there are only five "larger" islands. The highest point of the municipality is located in Frei, Freikollen at a height of 629 metres.
The island of Grip, located northwest of Kristiansund is also a part of the municipality. It was Norway's smallest island, and also one of the most remote municipalities until it merged with Kristiansund in 1964. Today the island of Grip holds status as a deserted fishing village, but in the summer season it is a popular tourist attraction due to the very special location and architecture. The smallest Stave church of Norway is also located on Grip.
Kristiansund is one of the most densely populated cities of Norway, having what is arguably the country's most urban small city center, due to the relatively small size of the islands on which it is built and the very constricted central harbour/town area of Kirkelandet.
Together they have a tournament called Nordiske Dager (Nordic Days).
Started in 1876 and still going strong is the Sundbåt ("Sound Boat"/"Strait Crossing Boat") shuttle service with a capacity of a few tens of passengers, travelling between the islands. The small motor ferry crosses the harbour from Kirk(e)landet to Innlandet, then goes on to Nordlandet, to Gomalandet, and back to Kirkelandet, repeating the round trip in half-hour intervals morning to evening on weekdays. The Sundbåt bears the distinction of being the world's oldest motorized regular public transport system in continuous service.
The road to Kristiansund from mainland Norway, National Road No. 70 (RV 70) is connected to European route E39 at the bridge/tunnel system called Krifast. After passing through the underwater tunnel from the central part of Krifast, RV 70 crosses Frei, and enters Kristiansund over the Omsund Bridge onto Nordlandet. The Nordsund Bridge brings the RV 70 to Gomalandet and its terminus in downtown at Kirkelandet. Another high bridge, the Sørsund Bridge, leads from Kirkelandet to Innlandet. The above mentioned E39 leads southwest to Molde and northeast via the E6 to Mid-Norway's principal city, Trondheim.
There is a car ferry going from Kirkelandet to Averøy, whose people have been commuting to town for many years for work as well as selling agriculture products. The ferry to Averøy connects Kristiansund to RV 64, which goes on via the scenic Atlanterhavsvegen to Molde. The ferry is scheduled to be replaced by the 5.7 km long underwater tunnel Atlanterhavstunnelen in December 2008. A second car ferry goes from Seivika on Nordlandet to Tustna in the northeast (road: RV 680), with further road and ferry connections to the islands Smøla and Hitra, and to Aure on the mainland.
Besides roads and car ferries and Kvernberget airport, communications to/from Kristiansund consist of the traditional coastal express Hurtigruten connecting coastal towns from Bergen in the south to Kirkenes in the north, and the high speed catamaran passenger service Kystekspressen to Trondheim. Another option to get to Kristiansund is to fly with Coast Air or SAS from several other Norwegian cities.
Kristiansund is known as the major bacalao city of Norway. Bacalao is made of salted, dried codfish, and has traditionally been exported in large amounts to Spain, Portugal and Latin America as food suitable during Lent. In recent years Kristiansund has become the major oil and gas city at the northwestern coast. Oil companies like Shell and StatoilHydro have offices in Kristiansund from where they serve their offshore installations at Haltenbanken (one of the northernmost underwater oil fields in the world).
Due to the city's heavy involvement in fish processing and international shipping, there used to be as many as seven consulates in Kristiansund, mainly to Latin countries. Currently, there are only five left: Britain, Finland, Germany, the Netherlands, and Portugal.