Sir John Henry Thorold, 12th Baronet (9 March 1842 – October 1922) was a British Conservative Party politician.
He was son of Sir John Charles Thorold, 11th Baronet and succeeded him in 1866, inheriting Syston Park.
He was elected at the 1865 general election as a Member of Parliament (MP) for the borough of Grantham in Lincolnshire, but did not stand again in 1868.
He was appointed High Sheriff of Lincolnshire for 1876–77.
He married Hon. Alexandrina Willoughby, daughter of Baron Middleton, on 3 February 1869, and they had five children: