Hosokawa Tama (1563–1600) was a Japanese noblewoman, daughter of Akechi Mitsuhide and wife of Hosokawa Tadaoka. She converted to Christianity in 1587 and received the Christian name Gracia.
In the war that followed the death of Toyotomi Hideyoshi, her husband sided with Tokugawa Ieyasu. When Tokugawa's rival Ishida Mitsunari attempted to take her hostage, she ordered the family retainer Ogasawara Shosai to kill her; he and the rest of household then committed seppuku. Their sacrifice led to the Hosokawa family joining the war on Tokugawa's side.
She was canonized by the Catholic Church in 1862.
She was used by James Clavell as the model for the character of Mariko in his novel Shogun.