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An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2‐aryl‐pyridines and 2‐aryl‐sp²‐nitrogen‐atom‐containing heterocycles with alkynes through rhodium(III)‐catalyzed CH activation and annulation under an O₂ atmosphere is described. A possible mechanism that involves the chelation‐assisted CH activation of the 2‐aryl‐pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five‐membered rhodacycle (I′). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.