Photopolymerization coupled with mask projection microstereolithography successfully generated various 3D printed phosphonium polymerized ionic liquids (PILs) with low UV light intensity requirements and high digital resolution. Varying phosphonium monomer concentration, diacrylate cross-linking comonomer, and display images enabled precise 3D design and polymeric properties. The resulting cross-linked phosphonium PIL objects exhibited a synergy of high thermal stability, tunable glass transition temperature, optical clarity, and ion conductivity, which are collectively well-suited for emerging electro-active membrane technologies. Ion conductivity measurements on printed objects revealed a systematic progression in conductivity with ionic liquid monomer content, and thermal properties and solvent extraction demonstrated the formation of a polymerized ionic liquid network, with gel fractions exceeding 95%.