Tachikawa (立川市, Tachikawa-shi) is a city located in the western portion of the Tokyo Metropolis, Japan.

Tokyo Metropolis Tachikawa has a humid subtropical climate (Köppen Cfa) characterized by warm summers and cool winters with light to no snowfall.

In the post-Meiji Restoration cadastral reform of July 22, 1878, the area became part of Kitatama District in Kanagawa Prefecture In the Meiji period, the opening of what would later become the Chuo Main Line in 1889 led to a large-scale land development and on April 1, 1889, with the establishment of the modern municipalities law, the village of Tachikawa was created.

[6][7] Tachikawa has a mayor-council form of government with a directly elected mayor and a unicameral city council of 28 members.

In terms of national politics, the city is part of Tokyo 21st district of the lower house of the Diet of Japan.

It is the central city of the populous "Tokyo Santama district", and commercial facilities such as department stores and offices are concentrated around Tachikawa Station.