Section III, Division 5 of the ASME Boiler & Pressure Vessel Code provides rules for designing high temperature nuclear components using inelastic analysis. However, the current Code does not provide guidance on suitable inelastic constitutive models to use with this design method nor does it provide Code qualified constitutive models for any of the high temperature Class A materials. This paper describes the development of an inelastic constitutive model for 316H steel, suitable for use with the Division 5 design procedures. The model captures the average response of all Code permissible 316 material as described by a large set of experimental data collected from the literature. The model uses a unified model to describe creep and rate dependent plasticity at high temperature that accounts for the experimentally-observed coupling of these deformation mechanisms. The goal is to incorporate the inelastic model developed here for 316H along with similar models for the other Class A, high temperature materials into Section III, Division 5 to facilitate the use of the design by inelastic analysis method.