  We report the violation of the Pauli limit due to intrinsic spin-orbit
coupling in SrTiO3 heterostructures. Via selective doping down to a few
nanometers, a two-dimensional superconductor is formed, geometrically
suppressing orbital pair-breaking. The spin-orbit scattering is exposed by the
robust in-plane superconducting upper critical field, exceeding the Pauli limit
by a factor of 4. Transport scattering times several orders of magnitude higher
than for conventional thin film superconductors enables a new regime to be
entered, where spin-orbit coupling effects arise non-perturbatively.
