"Custos regni" is a Latin phrase which means "keeper of the realm". It is an official title usually appointed by a monarch to someone who is responsible for the safety and security of the kingdom. Several synonyms can be used to describe this position, such as "steward", "protector", "guardian", "defender", "watchman", "keeper", and "sentinel". These words all convey the same meaning of being tasked with the responsibility of keeping the realm or kingdom safe and secure from external or internal threats. The "custos regni" is an important and prestigious role, and those who hold this position usually command a great amount of respect and authority.