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.
Her parents were the 23rd Baron de Ros and Lady Elizabeth Egerton.
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:
This biography of a baron or baroness in the Peerage of England is a stub.