chief guard; warden
Refers to the head of prison guards or the person in charge of a prison's security staff. In some contexts, it can be translated as 'warden', though the exact responsibilities may differ from the English term.
The chief guard explained the rules to the prisoners.
After many years of service, he was promoted to warden.
刑務官 is the official term for a correctional officer in Japan, a more formal and modern designation than 看守. 看守長 is the senior rank among such officers.
Compound of 看守 (かんしゅ, 'prison guard') and 長 (ちょう, 'head, chief').