We report the first observation of four-body breakup in electron dissociative recombination of a molecular ion: ${\mathrm{C}}_{2}\mathrm{D}_{5}{}^{+}$. In an ion storage ring experiment, the branching ratio for the process ${\mathrm{C}}_{2}\mathrm{D}_{5}{}^{+}+{\mathrm{e}}^{$-${}}$→${}{\mathrm{C}}_{2}{\mathrm{D}}_{2}+\mathrm{D}+\mathrm{D}+\mathrm{D}$ was determined to be 13%. This means that three covalent chemical bonds are broken as a result of the action of a single electron. This is the first time a four-body breakup of chemical bonds has been observed in a low-energy binary reaction.