Lady Mary Osborn, née Montagu, was the third daughter of George Montagu, 1st Earl of Halifax, K.B. (c. 1684-1739) and Lady Mary Lumley (1690-1726). She married, in 1740, Sir Danvers Osborn (see lot 137) and had two sons: George, who became 4th Baronet, and John. She died giving birth to John and they were raised by their grandmother, the Hon. Sarah Osborn.
For another portrait of a lady called Lady Mary Osborn, see lot 138.