Ōkubo Tadaoki (大久保 忠興, January 24, 1715 – November 22, 1764) was the 4th daimyō of Odawara Domain in Sagami Province, (modern-day Kanagawa Prefecture) in mid-Edo period Japan.
He held a number of minor ceremonial posts within the Tokugawa shogunate, but his tenure was noted for a steady deterioration in the state of the domain's finances, which were still suffering from the after effects of the Great Genroku earthquake and the Hōei eruption of Mount Fuji.
Tadaoki implemented various austerity measures, cumulating in the restructuring of 80 percent of the domain's retainers due to a state of near bankruptcy.
He retired from public life in 1763 with these issues unresolved, and died of illness on November 2, 1764, at the domain's Edo residence, His grave is at the clan temple of Saisho-ji in Setagaya, Tokyo.
Takaoki was married to a daughter of Yanagisawa Yoshisato, daimyō of Yamato-Kōriyama Domain in Yamato Province.