The mainland portion of Tokyo

The mainland portion of Tokyo lies northwest of Tokyo Bay and measures about 90 km east to west and 25 km north to south. Chiba Prefecture borders it to the east, Yamanashi to the west, Kanagawa to the south, and Saitama to the north. Mainland Tokyo is further subdivided into the special wards (occupying the eastern half) and the Tama area stretching westwards.

Also within the administrative boundaries of Tokyo Metropolis are two island chains in the Pacific Ocean directly south: the Izu Islands, and the Ogasawara Islands, which stretch more than 1,000 km away from the mainland. Because of these islands and mountainous regions to the west, Tokyo's overall population density figures far underrepresent the real figures for urban and suburban regions of Tokyo.