NTT may refer to:

• Nippon Telegraph and Telephone, a telephone company that dominates the telecommunication market in Japan
  • Its group companies can be found at Category:NTT
• New Technology Telescope, a 3.6m telescope located at La Silla Observatory, Chile
• Giant Robot (Giant Robot album), an album by the band Giant Robot and recording company NTT Records
• Number theoretic transform, a mathematical transform similar to the Discrete Fourier transform

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