C2H2 may mean:
Molecular formulae
The molecular formula C<sub>2</sub>H<sub>2</sub> (molar mass: 26.04 g/mol, exact mass: 26.01565 u) may refer to:
- Acetylene (or ethyne)
- Methylidenecarbene
- Vinylidene group
Transcription factors
- C2H2 zinc finger, short for Cys<sub>2</sub>His<sub>2</sub> a class of transcription factors with the small protein structural motif stabilised with Zinc ions