Bold Reason (1968–1985) was an American Thoroughbred racehorse and Champion broodmare sire. Bred by Harry Guggenheim, he was sired by Hail To Reason, the 1970 Leading sire in North America. His dam was Guggenheim's Lalun, who also produced Never Bend. He was bought as a yearling for $52,000 by William Levin at the 1969 Guggenheim dispersal sale. Retired to stud duty, Bold Reason was the leading broodmare sire in Great Britain & Ireland in 1984. Of his daughters' progeny, the most important was Sadler's Wells. Bold Reason died on November 14, 1985, at Samantha Farms in Old Westbury, New York.