Hosoya Jūdayū (細谷 十太夫, 1839–1907) was a Japanese samurai of the late Edo period, who served the Date clan of Sendai han, and was famous for his role in the Boshin War.
After the outbreak of the Boshin War, he was appointed a scout officer, and was active everywhere from Shōnai, to Shirakawa, to Yonezawa, even as far south as Mito.
In praise for his skill in guerilla warfare, Sendai lord Date Yoshikuni appointed him Captain of Pages, and bestowed on him the honorary name of Buichirō.
After the dissolution of the domains, Hosoya entered the field land reclamation, working together with such famous figures as Enomoto Takeaki, Nagai Naoyuki, and Sawa Tarōzaemon.
Entering the Imperial Japanese Army in the mid-1870s, he served as a lieutenant in the Seinan War, receiving the Order of the Rising Sun for his distinguished service in combat.