Seikadō Bunko Library, Private library in Okamoto, Japan

The Seikadō Bunko Library is a two-story reinforced-concrete building faced in scratch tile, designed by Sakurai Kotarō and completed in 1924 beside Yanosuke Iwasaki's tomb in Okamoto. Its symmetrical red-brown facade has a recessed central entrance arch up stone steps, a green metal roof over the door, white-framed windows and two tall brick chimneys behind a flat parapet. The style follows English suburban houses; the interior is normally closed to non-users.

Yanosuke Iwasaki founded the library in 1892 in his Kanda-Surugadai residence, naming it Seikadō after a phrase in the Shijing and collecting books to support his mentor Shigeno An'yaku. In 1907 he bought over 40,000 volumes from the Qing collector Lu Xinyuan. After his death in 1908, his son Koyata moved the library to Takanawa in 1911, then in 1924 built the present reinforced-concrete building beside his father's tomb, designed by Sakurai Kotarō.

The name Seikadō comes from the Shijing line "bian dou jing jia", meaning offerings arranged well before ancestral spirits; jing is glossed as good and jia as beautiful. Yanosuke Iwasaki, who had studied Chinese classics, took it as his study name. The library is open only to university students and above with a letter of introduction, by reservation.

The gallery section moved to Meiji Seimei Kan near Tokyo Station in October 2022, while the main library continues to operate from its original site in Okamoto. Visitors interested in both locations should plan for separate journeys between the two sites.

The library building, designed by Sakurai Kotarō in 1924, is closed to non-researchers, but the surrounding Okamoto Seikadō green space is open on weekdays from 9:30 a.m. to 4:30 p.m. It was maintained as the Iwasaki family garden until around 1945 and was chosen as one of the Setagaya 100 Views in 1984.