Spencer Horatio Walpole QC (11 September 1806 – 22 May 1898) was a British Conservative Party politician who served three times as Home Secretary in the administrations of Lord Derby.

He quickly gained a reputation in the House of Commons, and when the Tories came to power in early 1852 under Lord Derby, Walpole was appointed Home Secretary in the so-called "Who?

Walpole was again appointed Home Secretary, but resigned in January 1859 after disagreements over electoral reforms.

The Conservatives remained out of office for seven years, but in 1866 they again came to power under Derby, who made Walpole Home Secretary for the third time.

Walpole never held office again, but remained a Member of Parliament (MP) for Cambridge University until 1882.