Also known as a Type 3 civilization · K3
A Type III civilization — a galactic civilization — harnesses the energy output of an entire galaxy: hundreds of billions of stars working as a single coordinated system, on the order of 10³⁶ watts.
At Type III on the Kardashev scale, a civilization has expanded far beyond its home star. It has settled across the galaxy, likely harvesting energy from millions or billions of individual stars — a galaxy-wide network of Dyson swarms feeding a single civilization.
Reaching this scale implies near-light-speed travel or self-replicating probes, the ability to engineer at galactic distances, and structures that operate over thousands of light-years. Concepts include star-lifting across many systems, harnessing the central supermassive black hole, and kilonova-scale engineering.
A Type III civilization is deeply speculative — it would take vast spans of time to expand across a galaxy even at relativistic speeds. But within known physics, nothing strictly forbids it. It represents the upper end of the original Kardashev scale, beyond which only the hypothetical Type IV (universal) and Type V (multiversal) are imagined.
A Type III (galactic) civilization on the Kardashev scale can harness the energy of an entire galaxy — on the order of 10³⁶ watts, drawn from billions of stars across the galaxy.
Approximately 10³⁶ watts — about 4 × 10³⁶ W for a Milky-Way-sized galaxy. That is roughly ten billion times the energy of a Type II civilization.
Nothing in known physics forbids it, but it is highly speculative. Expanding across a galaxy would take enormous spans of time even with near-light-speed travel, so a Type III civilization remains a thought experiment for now.
Extensions to the original scale imagine a Type IV civilization harnessing the energy of the observable universe (~10⁴⁶ W) and a hypothetical Type V manipulating energy across multiple universes.
