Nielsine Nielsen (10 June 1850 – 8 October 1916) was the first female academic and physician in Denmark.

In 1868, she supported herself as a teacher at the Frøknerne Villemoes-Qvistgaards Institut in Copenhagen and worked as a governess in the provinces a couple of years.

In 1874, she corresponded with the Swedish female physician Charlotte Yhlen, who advised her to contact the Danish parliamentarian C. E. Fenger, who was known to support women's rights and who had previously supported the first female Danish telegrapher, Mathilde Fibiger.

In 1875, a royal decree issued the reform to allow women access to university education.

In 1904, she and Louise Nørlund, Birgitte Berg Nielsen and Alvilda Harbou Hoff became the first female members of the liberal party.