Abstract
The strong-field limit for the 2-form potential on an M5-brane yields a conformal chiral 2-form electrodynamics in six dimensions, with gauge-invariant self-interactions but no adjustable coupling constant; the stress tensor is that of a null fluid. Lorentz invariance can be made manifest via an interpretation as a tensionless 'space-filling M5-brane', or as a truncation of the infrared dynamics of an M5-brane in AdS(7) × S (4).