We discovered a pressure-induced metal-insulator transition in Ti
4O
7 which is a bipolaronic insulator at ambient pressure. In the pressure-induced metallic phase, the resistivity shows T
2-behavior att low temperatures. From the remarkably large magnitude of T
2-resistivity and its pressure dependence, we suggest that electron correlations are very likely the primal origin of the bipolaronic insulator phase of Ti
4O
7. In spite of early expectations, superconductivity was not observed down to 3 K.
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