AbstractPolymerization reactions with organic electron donors (OED) as initiators are presented herein. The metal‐free polymerization of various activated alkene and cyclic ester monomers was performed in short reaction times, under mild conditions, with small amounts of organic reducing agents, and without the need for co‐initiators or activation by photochemical, electrochemical, or other methods. Hence, OED initiators enabled the development of an efficient, rapid, room‐temperature process that meets the technical standards expected for industrial processes, such as energy savings, cost‐effectiveness and safety. Mechanistic investigations support an electron‐transfer initiation pathway that leads to the reduction of the monomer.