Sir Horace Darwin, KBE FRS (13 May 1851 – 22 September 1928) was an English engineer specializing in the design and manufacture of precision scientific instruments.

He was educated at a private school in Woodbridge, Suffolk, and at Trinity College, Cambridge, where he graduated BA in 1874.

They had one son and two daughters: He is buried at the Parish of the Ascension Burial Ground in Cambridge with his wife; his brother Sir Francis Darwin is interred in the same graveyard.

His other brother Sir George Darwin is buried in the Trumpington Extension Cemetery, Cambridge.

His family home, "the Orchard", in Huntingdon Road, Cambridge, is now the site of Murray Edwards College.