Norsk Ordbok (NO) is a comprehensive dictionary of written Norwegian (Nynorsk) and the Norwegian dialects, planned to twelve volumes and with four volumes published. The work will be completed in 2014. It is edited at the University of Oslo, published by the Norwegian publishing house Det Norske Samlaget, and financed by a direct government grant. Generally regarded as the definitive dictionary of Nynorsk, it defines around 25 0000 headwords per volume and will end at around 300 000 headwords. Illustrative quotations are drawn both from spoken Norwegian (with a geographical reference) and from literature.

Norsk Ordbok covers the neo-Norwegian period from 1600 onwards, though coverage for the first two centuries is scanty, consisting mainly of records of spoken Norwegian. Norsk Ordbok has good coverage of the period from 1850 onwards, the pioneer years of establishing Nynorsk as a written standard.

The collections on which Norsk Ordbok are based, were started in 1930, and comprise som 3,2 mill of literary exerpts and dialect quotations. The slip archives are now digitised, and supplied with a corpus of Nynorsk from 1850 onwards. The collections are accessible through Norsk Ordbok 2014 Search page.

Editing started in 1947, with volume 1 appearing in 1965, volume 2 in 1978, volume 3 in 1994 and volume 4 in 2003.

Norsk Ordbok was reorganised in 2002 with a view to speed up editing, and will be finished in 2014, to coincide with the bicentenary of the Norwegian constitution. Volume 5, the first volume to appear after the reorganisation, will be published in early 2005.