The molecular formula C<sub>6</sub>H<sub>4</sub>O<sub>4</sub> may refer to:
- Coumalic acid
- Dihydroxybenzoquinones
- 2,3-Dihydroxy-1,4-benzoquinone
- 2,5-Dihydroxy-1,4-benzoquinone
- 2,6-Dihydroxy-1,4-benzoquinone
- 3,4-Dihydroxy-1,2-benzoquinone
- 3,5-Dihydroxy-1,2-benzoquinone
- 3,6-Dihydroxy-1,2-benzoquinone
- 4,5-Dihydroxy-1,2-benzoquinone
- 5-Carboxyfurfuraldehyde
- 2-Furylglyoxylic acid
- 3-Furylglyoxylic acid
See also