Yoshimune TOKUGAWA was born on November 27, 1684 as the fourth son of Mitsusada TOKUGAWA who was the second lord of the Kishu Domain among the Tokugawa gosanke (as his parents' second son died at a young age, he sometimes counted as the third son).
貞享元年（1684年）10月21日、徳川御三家の紀州藩2代藩主・徳川光貞の四男として生まれる（次兄は早世しているため三男と数えられることもある）。