A general and highly chemo‐, regio‐, and stereoselective synthesis of α,β‐unsaturated aldehydes by a dominohydroformylation/aldol condensation reaction has been developed. A variety of olefins and aromatic aldehydes were efficiently converted into various substituted α,β‐unsaturated aldehydes in good to excellent yields in the presence of a rhodium phosphine/acid–base catalyst system. In view of the