Mary Dawson, Countess of Dartrey

Mary Frances Dawson, Countess of Dartrey, 24th Baroness de Ros of Helmsley (née FitzGerald-de Ros) (31 July 1854 – 4 May 1939) was a British peer. She was born in London. Her parents were Dudley FitzGerald-de Ros and Lady Elizabeth Egerton. Upon her father's death in 1907, Mary succeeded to the title.
The 25th Baroness married Anthony Dawson, 3rd Earl of Dartrey (1855–1933) in London on 2 October 1878. To them were born three daughters; the Barony of de Ros descended among their issue:
Lady Una Mary Dawson (born 1879), who became the 25th Baroness upon the termination of the abeyance in 1943.
Lady Maude Elizabeth Dawson (born 1882)
Lady Eleanor Charlotte Augusta Dawson (born 1885)