Truxinic acids are any of several stereoisomeric cyclic dicarboxylic acids with the formula (C<sub>6</sub>H<sub>5</sub>)<sub>2</sub>C<sub>4</sub>H<sub>4</sub>(COOH)<sub>2</sub>, found in various plants. They are obtained by a photochemical cycloaddition from cinnamic acid, where the two trans alkenes react head-to-head.
Ten stereoisomers are possible.