Iwatsuki Domain was a feudal domain under the Tokugawa shogunate of Edo period Japan, in Musashi Province, Japan. It was centered on Iwatsuki Castle in what is now part of Iwatsuki-ku, Saitama.

Musashi Province was a province of Japan, which today comprises Tokyo Metropolis, most of Saitama Prefecture and part of Kanagawa Prefecture. It was sometimes called Bushū (武州). The province encompassed Kawasaki and Yokohama. Musashi bordered on Kai, Kōzuke, Sagami, Shimōsa, and Shimotsuke Provinces.