Henry Thomas "Harry" Blackstaffe (28 July 1868 – 22 August 1951) was a British rower who competed in the 1908 Summer Olympics.
Blackstaffe was born in Islington, London, and became a butcher. He was a long-standing member of Vesta Rowing Club in Putney and also a cross-country runner who represented South London Harriers in the National Championships. As a single sculler he won nine victories in the London Cup at the Metropolitan Regatta. He first won the Wingfield Sculls in 1897 but in 1898, 1899 and 1900 was beaten by Benjamin Hunting Howell. He won again in 1901 defeating Saint George Ashe and Arthur Cloutte. He lost to Cloutte in 1902 and to Ashe in 1904, but beat them both in 1905 and 1906. At first he had difficulty in having his entry accepted for Henley Royal Regatta but competed in the Diamond Challenge Sculls in 1905 when he lost to Frederick Septimus Kelly. In 1906 he won the Diamond Sculls beating Captain Darell. In 1908 he won the Wingfield Sculls again and his ninth London Cup, but his major success was to win the gold medal in the single sculls, rowing at the 1908 Summer Olympics. He was aged forty and his opponent in the final Alexander McCulloch was exactly half his age and had won Diamonds that year. The final was considered the finest race of the Olympic Regatta and was virtually level until the last 50 yards when Blackstaffe held on to a light advantage to become the oldest sculling champion in Olympic history
After this victory, Blackstaffe retired and was made a Freeman of the City of London. He was later senior life vice-president of the Amateur Rowing Association.
Blackstaffe died at West Wickham,at the age of 83.