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.

Sagami Province was a province of Japan located in what is today the central and western Kanagawa Prefecture. Sagami Province bordered the provinces of Izu, Musashi, and Suruga. It had access to the Pacific Ocean through Sagami Bay. However, most of the present-day cities of Yokohama and Kawasaki, now part of Kanagawa Prefecture, were not in Sagami, but rather, in Musashi Province. Its abbreviated form name was Sōshū (相州).