From the 1840s, some writers experimented with a Norwegianized Danish by incorporating words that were descriptive of Norwegian scenery and folk life, and adopting a more Norwegian syntax. Knud Knudsen proposed to change spelling and inflection in accordance with the Dano-Norwegian koiné, known as "cultivated everyday speech." A small adjustment in this direction was implemented in the first official reform of Danish language in Norway in 1862 and more extensively after his death in two official reforms in 1907 and 1917.

Meanwhile, a nationalistic movement strove for the development of a new written Norwegian. Ivar Aasen, a self-taught linguist, began his work to create a new Norwegian language at the age of 22. He traveled around the country, comparing the dialects in different regions, and examined the development of Icelandic, which had largely escaped the influences Norwegian had come under. He called his work, which was published in several books from 1848 to 1873, Landsmål, meaning national language. The name "Landsmål" is sometimes interpreted as "rural language" or "country language," but this was clearly not Aasen's intended meaning.

The name of the Danish language in Norway was a topic of hot dispute through the 19th century. Its proponents claimed that it was a language common to Norway and Denmark, and no more Danish than Norwegian. The proponents of Landsmål thought that the Danish character of the language should not be concealed. In 1899, Bjørnstjerne Bjørnson proposed the neutral name Riksmål, meaning national language like Landsmål, and this was officially adopted along with the 1907 spelling reform. The name "Riksmål" is sometimes interpreted as "state language," but this meaning is secondary at best, compare to Danish rigsmål from where the name was borrowed.

After the personal union with Sweden was dissolved in 1905, both languages were developed further and reached what is now considered their classic forms after a reform in 1917. Riksmål was in 1929 officially renamed Bokmål (literally "Book language"), and Landsmål to Nynorsk (literally "New Norwegian"). A proposition to substitute Dano-Norwegian for Bokmål lost in parliament by a single vote. The name Nynorsk, the linguistic term for Modern Norwegian, was chosen for contrast to Danish and emphasis on the historical connection to Old Norwegian. Today this meaning is often lost, and it is commonly mistaken as a "new" Norwegian in contrast to the "real" Norwegian Bokmål.

Bokmål and Nynorsk were made closer by a reform in 1938. This was a result of a state policy to merge Nynorsk and Bokmål into one language, called "Samnorsk" (Common Norwegian). A 1946 poll showed that this policy was supported by 79% of Norwegians at the time. However, opponents of the official policy still managed to create a massive protest movement against Samnorsk in the 1950s, fighting in particular the use of "radical" forms in Bokmål text books in schools. In the reform in 1959, the 1938 reform was partially reversed in Bokmål, but Nynorsk was changed further towards Bokmål. Since then Bokmål has reverted even further toward traditional Riksmål, while Nynorsk still adheres to the 1959 standard. Therefore a small minority of Nynorsk enthusiasts uses a more conservative standard called Høgnorsk. The Samnorsk policy had little influence after 1960, and was officially abandoned in 2002.