A room or designated area for changing clothes, such as in a gym, pool, or workplace. Often synonymous with 更衣室, though 更衣所 may imply a slightly more functional or temporary space.
See also: 更衣室
I changed into my swimsuit in the pool's changing room.
The factory has a changing room for employees.
Compound of 更衣 (kōi, 'changing clothes') + 所 (sho, 'place'). The exact historical derivation is uncertain, but the word follows a standard Sino-Japanese pattern for naming facilities.