The development of 3D printing technologies and the requirement for more sustainable 3D printing materials is constantly growing. However, ensuring both sustainability and performance of the new materials is crucial to replace current fossil-based polymers. Here, a bio-based UV-curable resin is produced in high yield from gallic acid (GA), a natural polyphenolic compound, by means of rapid and efficient microwave-assisted methacrylation (5 min heating time and 10 min at 130 °C). The successful microwave-assisted methacrylation with a high degree of substitution is confirmed by Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy. The radical UV-photopolymerization of the methacrylated gallic acid (MGA) is further investigated by real-time FTIR and differential scanning photo calorimetry (photo-DSC) analyses, clearly demonstrating the high photo-reactivity of MGA. Moreover, the %gel assessment demonstrates the formation of highly insoluble fractions after the UV-curing, with 98% gel content. The photo-rheology and rheology support the suitability of MGA for light-assisted 3D printing. Indeed, a honeycomb and a hollow cube are 3D printed by means of the digital light processing 3D printing technique with high accuracy in a small scale. Finally, the cured-MGA illustrates high Tg and thermal stability.