Tomakomai is a city and port located in the Iburi Subprefecture of Hokkaido, Japan. It serves as the largest city within its subprefecture and ranks as the fourth largest city in the Hokkaido region.
As of July 31, 2023, the city had an estimated population of 167,372 residents living in 83,836 households. The total land area of Tomakomai is 561.57 km² (216.82 sq mi), resulting in a population density of approximately 298 persons per km².