Boris Karloff (23 November 1887 – 2 February 1969) was an English actor who emigrated to Canada in the 1910s. He is best remembered for his roles in horror films and his portrayal of Frankenstein's monster in the 1931 film Frankenstein, 1935 film Bride of Frankenstein, and 1939 film Son of Frankenstein. His popularity following Frankenstein in the early 1930s was such that for a brief time he was billed simply as "Karloff" or, on some movie posters, "Karloff the Uncanny".

Karloff was born William Henry Pratt at 36 Forest Hill Road, East Dulwich, London, England, where a blue plaque can now be seen. He was brought up in Enfield. His paternal grandmother was Eliza Julia (Edwards) Pratt, a sister of Anna Leonowens, whose tales about life in the royal court of Siam (now Thailand) were the basis of the musical The King and I. Her maternal grandmother was of Indian origin, being from Kolkata. In 1845, Anna's 15-year-old sister, Eliza Julia Edwards, married Edward John Pratt, a 38-year-old Anglo-Indian civil servant who had served in the Indian Navy. Eliza and Edward had a son, Edward John Pratt, Jr., who in 1887, with his wife, Eliza Sarah Millard, had a son named William Henry Pratt, who later became known as Boris Karloff. Because Pratt Sr. was an Anglo-Indian, Anna never approved of Eliza's marriage, and her disconnect from the family was so complete that decades later, when a Pratt relative contacted her, she replied threatening suicide if he persisted.

Research for a new biography has shown the actor was not orphaned in his youth, as has always been believed. Following his mother's death he was raised by his elder brothers and sister and attended Enfield Grammar School before moving to Uppingham School and Merchant Taylors' School, Northwood, and eventually King's College London. Karloff's first goal in life was to join the foreign service — his brother, Sir John Henry Pratt, became a distinguished British diplomat — but instead he fell into acting.