A person who resides in a particular place, often used in official or formal contexts such as registration, surveys, or community notices.
この地域の在住者は、来月の防災訓練に参加してください。
Residents of this area, please participate in next month's disaster drill.
在住者 emphasizes currently residing in a country or region (e.g. 海外在住者), while 居住者 more generally refers to anyone living at a given address or location.
Compound of 在住 (ざいじゅう, 'residing') + 者 (しゃ, 'person'). 在住 is itself from 在 (ざい, 'to exist' or 'to be in a place') and 住 (じゅう, 'to live').