Marian Sarah Ogilvie Farquharson, FLS, FRMS (née Ridley, 2 July 1846 – 20 April 1912) was a British naturalist and women's rights activist.

In 1883, she married Robert Francis Ogilvie Farquharson from near Alford, Aberdeenshire, where she moved to live with him on the Haughton estate.

[2] After her husband's death in 1890, Farquharson began active campaigning for women's rights for full fellowship and participation of learned societies.

After its former president John Lubbock, 1st Baron Avebury resubmitted the petition on her behalf, the society eventually declined the proposal on the basis that it was doubtful its royal charter could be applied to women.

In 1903, the Society decided to seek a supplementary charter from the King explicitly allowing women fellows.