John Winston Spencer-Churchill, 7th Duke of Marlborough, KG, PC (2 June 1822 – 4 July 1883), styled Earl of Sunderland from 1822 to 1840 and Marquess of Blandford from 1840 to 1857, was a British Conservative cabinet minister, politician, peer, and nobleman.

He was responsible for the "Blandford Act" of 1856, enabling populous parishes to be divided for purposes of Church work.

[5] Spencer-Churchill was president of The Shipwrecked Fishermen and Mariners' Royal Benevolent Society for many years.

They had eleven children: Marlborough died on 4 July 1883, aged 61, and was succeeded in the title by his eldest son, George.

Marlborough was portrayed by Cyril Luckham in the 1974 Thames Television mini-series Jennie: Lady Randolph Churchill.