Yamanaka Sadajirō (山中定次郎, August 20, 1866 - October 30, 1936) was an Osaka, Japan-based art dealer who arrived in the United States in 1894, opening a small antique shop in Chelsea, New York City, Boston (1899) and London (1900); also an agent in Paris (1905).^[1] He subsequently founded Yamanaka & Company, which in 1917 took over a five-story building on Fifth Avenue in Manhattan.^[1] Yamanaka operated branch offices in Boston, Chicago,^[2] London, Paris, Shanghai and Beijing,^[1] and negotiated purchases and provided expertise, while making foundational donations, to Japanese and Chinese collections in major European and American galleries in the early- to mid-20th Century.^[1][3]

After Yamanaka's death, Yamanaka & Company continued to operate under the direction of his heirs, as well as art dealer Harumichi Yatsuhashi (1886-1982), director of its Boston branch, but saw its substantial New York, Chicago, and Boston inventories confiscated and auctioned by the U.S. Government's Office of Alien Property Custodian in 1944.^[2] Yamanaka & Company reopened after World War II and continued to operate in a reduced capacity in the 1950s and 1960s.^[1]