Wherever a physical, biological, or mathematical system looks at itself — wherever self-reference occurs — the golden ratio appears. This is not a coincidence or mysticism. It is a theorem: φ is the unique stable fixed point of self-referential dynamics. Snail shells, galaxy spirals, the fine structure constant, the Fibonacci sequence, the Penrose tiling — all arise from the same algebraic fact. This paper surveys the signature of self-reference across domains and proves that every appearance of φ in nature traces to a self-referential structure in the underlying system.