The title Baron Greystock (or Greystoke) has been created twice in the Peerage of England. It was first created when John de Greystock was summoned to parliament in 1295 and it became extinct on his death. It was next created for Sir Ralph de Greystock in 1321, and went into abeyance in 1569, after it had passed into the Dacre family through the marriage of Thomas Dacre, 2nd Baron Dacre to Elizabeth de Greystoke, 6th Baroness Greystoke.
The title Lord Fitzwilliam seems to have been associated with the second creation, but this matter is unclear.
Barons Greystoke, first creation (1295)
- John de Greystoke, 1st Baron Greystock (1264–1306) (extinct)
Barons Greystoke, second creation (1321)
- Ralph de Greystoke, 1st Baron Greystoke (1299–1323)
- William de Greystoke, 2nd Baron Greystoke (1320–1358)
- Ralph de Greystoke, 3rd Baron Greystoke (1352–1417)
- John de Greystoke, 4th Baron Greystoke (1390–1436)
- Ralph de Greystoke, 5th Baron Greystoke (1414–1487)
- Elizabeth de Greystoke, 6th Baroness Greystoke suo jure (10 July 1471 – 14 August 1516)
- William Dacre, 7th Baron Greystoke (1500–1563)
- Thomas Dacre, 8th Baron Greystoke (c. 1526–1566)
- George Dacre, 9th Baron Greystoke (1561–1569) (abeyant)