THD may refer to:
- Total harmonic distortion, a measure of the distortion of an audio signal
- Total Hi Def (Total HD), an optical disc format
- Th.D. or D.Th. or D.Theol., a Doctor of Theology degree
- Thames Ditton railway station, Surrey, National Rail station code
- THD Electronics, a guitar amplifier manufacturer
- Transanal hemorrhoidal dearterialization, a surgical procedure
- That Handsome Devil, an American alternative rock band
- The IATA airport code for Thọ Xuân Airport
- The ICAO airline code for Thai Smile
- Transmitting Heading Device