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 24th 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:

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