Nippon Telegraph and Telephone Corporation (also known as Nippon Telegraph and Telephone Corporation, Japanese: Nippon Telegraph and Telephone Corporation, English: NIPPON TELEGRAPH & TELEPHONE, abbreviated as NTT Corporation) is one of the world's largest telecommunications companies, headquartered in Tokyo, Japan. NTT Corporation was formerly known as Nippon Telegraph and Telephone Corporation (NTT), one of the three subsidiary Japanese companies . NTT DoCoMo, East Japan Telecom & Telephone, West Japan Telecom & Telephone, and NTT DATA.