operator; manager; administrator
Refers to a person or entity that runs or manages an organization, service, website, event, etc. Neutral term; can be used in business, tech, and general contexts.
I will contact the operator of this site.
The event manager oversees the flow on the day.
管理者 emphasizes administrative control and maintenance (e.g., system administrator), whereas 運営者 focuses on the active running or operation of something.
Compound of 運営 (うんえい, 'operation, management') + 者 (しゃ, 'person'). The word is a straightforward Sino-Japanese formation.