The molecular formula C9H8O4 (molar mass: 180.15 g/mol, exact mass: 180.0423 u) may refer to:
- Acetozone
- Aspirin
- 4-Hydroxyphenylpyruvic acid, a natural phenol
- Dihydroxycinnamic acids:
- Caffeic acid (3,4-Dihydroxycinnamic acid)
- Umbellic acid (2,4-dihydroxycinnamic acid)
- 2,3-Dihydroxycinnamic acid
- 2,5-Dihydroxycinnamic acid
- 3,5-Dihydroxycinnamic acid
- Homophthalic acid
- Monomethyl phthalate
- Uvitic acid