Martha Ottomine Steen Tynæs (1870–1930) was a Norwegian feminist, social worker and politician.
She was one of the pioneering members of the Norwegian Labour Party's Women's Federation which she chaired almost without interruption from 1904 to 1920.
From 1901 to 1918 she served as the only woman on the Labour Party's central committee and chaired Christiania's city council from 1908 to 1919.
In 1909, she became the first Norwegian women to become a parliamentary candidate when she stood in the constituency of Hammersborg, although she was not elected.