We report the synthesis and molecular characterization of structurally defined, sulfo-phenylated, oligo- and polyphenylenes that incorporate a novel tetrasulfonic acid bistetracydone monomer. The utility of this monomer in the [4 + 2] Diels-Alder cycloaddition to produce well-defined, sulfonated oligophenylenes and prefunctionalized polyphenylene homopolymers is demonstrated. Characterization of the oligophenylenes indicates formation of the meta-meta and para-para adducts in a similar to 1:1 ratio. These functionalized monomers and their subsequent coupling provide a route to prepare novel, sterically encumbered, sulfonated polyphenylenes possessing unprecedented structural control.