The Astro-Mycelium Hypothesis offers a unified, biologically grounded explanation for some of the most persistent anomalies in UAP/UFO phenomena: seamless transmedium objects, extreme non-inertial maneuvers, nuclear affinity, shape-shifting forms, electromagnetic interactions, and even the patterns of close encounters and crash retrievals. By reframing UAPs not as manufactured metallic craft from distant stars but as highly evolved, macroscopic analogs to terrestrial fungi and slime molds (originating in deep space or asteroid belts), this hypothesis resolves many physical, biological, and logistical contradictions in UAP lore. Some elements include: - Chitinous bio-hulls and decentralized mycelial intelligence for seamless, brainless operation.- Adaptive hydrostatic morphology explaining disks, tic-tacs, orbs, and jellyfish-like forms.- Non-kinetic propulsion via radiation pressure bio-sails, spore-like expulsion, and electrostatic levitation.- Radiotrophic foraging as the ecological driver behind nuclear site affinity. The framework draws on established Earth biology (e.g., Chernobyl radiotrophic fungi, Physarum polycephalum problem-solving, Pilobolus spore jets) and basic physics, while offering testable predictions (e.g., spectral signatures, filament residues). Deeper speculations on abductions and "Grey" avatars are presented as extensions. This preprint establishes priority for the hypothesis prior to potential formal submission or expansion into a longer work.