Maria Emma Gray (1787–1876), was an English conchologist and algologist.
Gray was born in 1787 at Greenwich Hospital, where her father, Lieutenant Henry Smith, R.N., was then resident. She married in 1810 Francis Edward Gray, who died four years later, and had by him two daughters, who survived her. In 1826 she married his second cousin, John Edward Gray. She greatly assisted her second husband in his scientific work, especially by her drawings. Between 1842 and 1874 she published privately five volumes of etchings, entitled Figures of Molluscan Animals for the use of Students, and she mounted and arranged most of the Cuming collection of shells in the British Museum.
She was also much attached to the study of algae, arranging many sets for presentation to schools throughout the country so as to encourage the pursuit of this subject. Her own collection was bequeathed to the Cambridge University Museum, and her assistance in this branch of his studies was commemorated by her husband in 1866 in the algae genus Grayemma. Similarly, he named two species of lizards in her honor: Calotes maria and Calotes emma. He also had a bronze medallion struck in 1863, bearing both their portraits, a copy of which is in the possession of the Linnean Society. Gray survived her husband by a year, dying 9 December 1876.