Ophir appears 12x in the OT, once as the name of a person—beyond that fact that he was one of the sons of Joktan, we know nothing about him (Gen 10:29 & 1 Chron 1:23)—and the other references as a place famous for its gold (Job 22:24; 28:16; Psm 45:9; Isa 13:12).
Ophir as a source of gold is first noted in connection with David's generous provisions out of his personal treasury of, among a great deal of other precious metals and stones, "three thousand talents of gold (gold of Ophir)" for the construction of the temple that his son Solomon was to build (1 Chron 29:4). Subsequently, a joint-venture between Solomon and Hiram, king of Tyre, brought back more gold as well a great deal of other precious materials (1 Ki 9:28-10:11 & 2 Chron 8:18-9:10). King Jehoshaphat attempt to duplicate the venture but his fleet were wreck before they could set out (1 Ki 22:48). A reference to the gold of Ophir has been found on a preexilic sherd uncovered at Tell Qasileh. The inscription reads, "Gold of Ophir for Bethhoron, thirty shekels" (B. Maisier, "Two Hebrew ostraca from Tell Qasile," JNES 10:265-67). This find indicates that at least one king after Jehoshaphat was successful in procuring additional Ophir gold." (TWOT).
The location of Ophir has never been identified. A number of theories have attempted to do so by identifying what other goods were brought back along with the gold (almug wood, ivory, and apes and baboons, e.g., are mentioned in 1 Ki 10:11ff) and the length of the journey made by Hiram's men (1 Ki 10:22 suggests about three years). Proposals include Somalia, the south-west coast of the Arabian Peninsula (Yemen), and India.