John Ernest Greaves CBE (30 November 1847 – 27 February 1945) was a wealthy Welsh slate mine owner and Lord Lieutenant of Caernarvonshire.

He was born on 30 November 1847 at Tan-yr-allt, Tremadog, the son of John Whitehead Greaves, who had been instrumental in the development of the slate industry around Blaenau Ffestiniog.

He spent much of his childhood at his father's Llechwedd quarry and was educated at schools in Warwickshire, Edinburgh and Dorset before going to Worcester College, Oxford, where he matriculated in 1867.

[1] On his father's death he inherited a half share in the business and made his brother Richard Methuen Greaves the General Manager.

[3] He was very involved in public affairs as President of the North Wales branch of the NSPCC, and Chairman of the Quarter Sessions and Alderman of Caernarvon County Council.