The molecular formula C5H9NO3 (molar mass : 131.13 g/mol) may refer to:
- Aminolevulinic acid, first compound in the porphyrin synthesis pathway
- Glutamate-1-semialdehyde
- Glutamate-5-semialdehyde
- Hydroxyproline
The molecular formula C5H9NO3 (molar mass : 131.13 g/mol) may refer to: