Ralph Thoresby (16 August 1658 – 16 October 1725) was an antiquarian, who was born in Leeds and is widely credited with being the first historian of that city. Besides being a merchant, he was a nonconformist, fellow of the Royal Society, diarist, author, common-councilman in the Corporation of Leeds, and museum keeper.

Ralph Thoresby was the son of John Thoresby, a Leeds merchant who for a time was an officer under Fairfax during the English Civil War, and was by inclination an antiquarian; and of his wife Ruth (b. Ruth Idle, from Bulmer, near York).

According to the preface of The Diary of Ralph Thoresby F.R.S., father and son were alike, deeply religious and both with strong attachments to antiquarian pursuits. John Thoresby established for himself a museum of coins and medals, purchasing at great expense two pre-existing collections owned by the Fairfax family and another family called Stonehouse.

Ralph was educated at Leeds Grammar School, and on the death of his older brother became the eldest son of the family. He was sent at the age of eighteen to the house of a relation in London, as part of his grooming as a merchant. He maintained a diary from this point, fairly consistently, throughout the rest of his life; an edited version was published in 1830.

From July 1678 to February 1679, he resided in Holland, to complete his mercantile training. From March 1679 until the end of his life he lived in Leeds.

He inherited his father's business and museum upon the former's death on 31 October 1679, and provided for his younger brother and sister.

In 1683, he was prosecuted as a nonconformist. Evidently this was not a great setback since in 1684 he "took his freedom" of (joined) the Eastland and Hamburgh Companies, two of the five regulated companies for foreign commerce (the others being the Muscovy, Levant and African Companies).

On 25 February 1685 he married Anna Sykes, daughter of Richard Sykes, one of the lords of the manor of Leeds.