Prostitution () in Norway is illegal, in that offering consideration for sexual services (seksuelle tjenester or seksuelle ytelser), but not selling sex, is a criminal offence. The Norwegian law prohibiting the buying of sexual services (sexkjøpsloven) came into effect on January 1, 2009, following the passing of new legislation by the Norwegian parliament (Storting) in November 2008. Soliciting and advertising sexual services is also illegal under the Norwegian Criminal Code (Straffeloven) section 378 and section 202(3).
In early times proscription of sex work fell under more general laws on fornication and adultery, particularly after the Reformation. Around this time, sexual acts started to be moved from civil law (largely with fines) to criminal law. for instance in one part of Mediaeval law, the Frostathing Law, it is stated "if a woman lies with a man whom she is not allowed to possess, she owes a fine of three marks, just as he does with whom she lies". Regulation of sexuality in the High Middle Ages was largely a function of the Church, for whom only heterosexual sexual relations within marriage was acceptable. Despite this sex work was not considered amongst the most serious sexual crimes, but was frequently associated with other nuisances such as gambling, drinking and causing a disturbance.
Sex work was criminalised in Norway with the introduction of the new Criminal Code (Norske Lov) in 1842, but was made legal again when the Penal Code (Straffeloven) was revised in 1902, when the prohibition of both the sale and purchase of sex was lifted. However even during that time it was actually tolerated and regulated in practice, in the larger cities such as Oslo, Bergen and Trondheim. While sex work was defined as an immoral vice, it was street sex work that was especially frowned upon, being visible. It was also considered important to distinguish between 'decent' and 'indecent' women. The regulation of sex work in Europe (Regulationism) was closely tied to the concept that prostitution was a source of venereal disease, requiring medical supervision. This form of regulation first appeared in Bergen, then the largest Norwegian municipality, in 1816, in (what is now known as) Oslo in 1840, and Trondheim in 1844. Regulation was at least on the surface contrary to the Penal Code which had made fornication and hence prostitution a criminal offence in 1842. In practice the latter law was considered only to apply to males.