| Honorific Prefix: | The Right Honourable |
| The Countess of Kent The Baroness Lucas | |
| Succession: | Baroness Lucas of Crudwell |
| Reign: | 7 May 1663 – 1 November 1702 |
| Predecessor: | |
| Successor: | Henry Grey |
| Birth Name: | Mary Lucas |
| Birth Date: | In 17th century |
| Death Date: | 1 November 1702 |
| Burial Place: | Flitton |
| Noble Family: | Lucas Grey (by marriage) |
| Spouse: | Anthony Grey, 11th Earl of Kent |
| Issue: |
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| Father: | John Lucas, 1st Baron Lucas of Shenfield |
| Mother: | Anne Nevill |
Mary Lucas, suo jure 1st Baroness Lucas of Crudwell (died 1 November 1702), also called Mary Grey, Countess of Kent, was an English peeress in her own right.
Mary Lucas was the only daughter of John Lucas, 1st Baron Lucas of Shenfield, Essex (1606–1671) and Anne Nevill. She had a brother named John, who was born in 1633, but he died young. As a result, she was the sole heiress of her father.
On 2 March 1662/1663, Mary Lucas married Anthony Grey, 11th Earl of Kent. By marriage, she became Countess of Kent. Mary and Anthony had two children:
On 7 tháng 5 năm 1663, according to the request of John Lucas, 1st Baron Lucas of Shenfield, father of the Countess of Kent, Mary was created suo jure Baroness Lucas of Crudwell by Charles II of England in the Peerage of England. This new creation was granted a special remainder to Mary's heirs male by her husband Anthony Grey, 11th Earl of Kent, and failing which, to her heirs female without division. This was a unique remainder for the English peerage as it can not fall into abeyance between female co-heiresses but is inherited by the senior co-heiress alone.
Mary Lucas, Countess of Kent and Baroness Lucas, passed away on 1 November 1702 and was succeeded in the barony by her eldest son Henry Grey, who in 19 August 1702 also succeeded his father as 12th Earl of Kent and was created Duke of Kent on 28 April 1710. Mary and her husband was buried at Flitton.[1] [2]