We present the first demonstration of a nanofabricated photonic crystal made from the magnetic material yttrium iron garnet (YIG). YIG is a compelling material for quantum technologies due to its unique magnetic and optical properties; however, experiments involving YIG have primarily been limited to millimeter-scale spheres. The successful nanofabrication of YIG structures opens new avenues for advancing quantum technology applications. Notably, the ability to co-localize magnons, phonons, and optical photons within a nanostructured environment paves the way for novel approaches in quantum information processing, including quantum wavelength transduction and enhanced magnon-photon interactions. This work marks a significant step toward integrating YIG-based devices into scalable quantum platforms.