Futabayama Sadaji (??? ??; February 9, 1912 – December 16, 1968), born as Akiyoshi Sadaji (?? ??) in Oita Prefecture, Japan, was the 35th yokozuna in sumo wrestling, from 1937 until 1945.
He won twelve yusho or top division championships and had a winning streak of 69 consecutive bouts, an all-time record.
Despite his dominance he was extremely popular with the public.
After his retirement he was head coach of Tokitsukaze stable and chairman of the Japan Sumo Association.