Tajarhi was a star that was located a number of parsecs away from Earth and the Sol system, in Federation space, near the border between the Alpha and Beta Quadrants. Tajarhi is in the general vicinity of Pari, Oblik, Horok and the Alferaz system. (TOS reference: Star Fleet Technical Manual)

The Tajarhi system was inhabited by a Federation population. As a representative of the Federation Council, Doctor Jason Crandall mediated a number of negotiations at Tajarhi. Through Crandall's malpractice as a diplomat, a dispute got out of hand, leading to a number of deaths that were sometimes referred to as the Tajarhi disaster. Mentally unhinged, Crandall blamed others for the incident and was placed by the Federation government in different roles as a science advisor. (TOS novel: Chain of Attack)

The Federation starship USS Tajarhi was named for this location. (TOS reference: Star Fleet Technical Manual)