Mediator is a series of six books written by Meg Cabot originally under the pseudonym of Jenny Carol;

By analogy, someone who channels contact between mortals and divinity; e.g. in the Christian faith, Christ is sometimes referred to as the mediator between humanity and God the Father (external link: [1])

Médiateur de la Confédération Helvétique was Napoleon I Bonaparte's title as hegemon in French-occupied Switzerland;

Mediator variable in statistics;

Mediator design pattern in computer science;

A neutral party who assists in negotiations and conflict resolution, the process being known as mediation

The multiprotein Mediator complex in Biology was discovered by Roger D. Kornberg;