Umlaut may refer to:
- Diaeresis (diacritic), a pair of dots ( ¨ ) above a vowel, used in various languages
- Metal umlaut, the same diacritic in names of heavy metal or hard rock bands for effect
- I-mutation or umlaut, historic vowel fronting or raising in any language
- Germanic umlaut, this process in Germanic languages
- Affection (linguistics), this process in Celtic languages
- Regressive vowel harmony
- Umlaut vowel can refer to any front rounded vowel:
- Close front rounded vowel
- Close-mid front rounded vowel
- Open-mid front rounded vowel
- Open front rounded vowel
- Lars Umlaut, a character playable in the Guitar Hero series of music video games
- Umläut, Clinton McKinnon's experimental Australian rock band
- Umlaut (software), an open source link resolver front-end for libraries