We designed and synthesized cyclic quinoline tetramers (TEtraQuinolines; TEQs), a new family of conjugated macrocycles that contain four inwardly oriented nitrogen atoms. Due to their excessive structural rigidity, indirect construction via a cyclic diamide precursor was required, and subsequent ring reinforcement under judiciously chosen conditions furnished these TEQs. The crystallographic analysis of C2-symmetric substituted TEQs revealed a steep saddle shape, which is highly rigid and maintains its stereochemical integrity even at 240 °C. Interestingly, these inherently fluorescence-silent TEQs become strongly emissive upon protonation or addition of Zn(II) cations, implying potential utility as structurally robust pH or Zn probes. A systematic complexation study revealed that these TEQs can serve as tetradentate ligands for a series of transition metals, and that the obtained complexes display high kinetic stability towards cation exchange and protonation. A TEQ/Fe(II) complex exhibits catalytic activity in the oxidation of tetrahydroisoquinolines, indoline, and dihydroanthracenes, whereby catalyst loadings as low as 0.1 mol% promote these reactions effectively. Given that polypyridyl/transition metal complexes are widely used in high-value-added chemical transformations (e.g., CO2 reduction and photochemical water splitting), the rigid and robust tetradentate ligand TEQ represents a new platform for catalyst design and molecular engineering.