Abstract
Previously, it was shown that Schrödinger's theory can be derived from a potential flow Lagrangian provided a Fisher information term is added. This approach was later expanded to Pauli's theory of an electron with spin, which required a Clebsch flow Lagrangian with non-zero vorticity. Here, we use the recent relativistic flow Lagrangian to represent Dirac's theory with the addition of a Lorentz invariant Fisher information term as is required by quantum mechanics.