Physics-based compact electrothermal macromodels of standard cells are developed for fast dynamic simulation of three-dimensional integrated circuits (3DICs). Such circuits can have high thermal densities and thermal effects often limit their performance. The macromodels developed here use fewer state-variables than a discrete transistor-level implementation while retaining transistor-level accuracy. This results in significant speed-up over transistor-level simulation for large-scale circuits. The macromodel-based methodology enables robust and significantly faster dynamic electrothermal simulation over the long times required for thermal transients to subside. Consequently, transient junction temperature can be examined in the design phase. Simulated junction and measured surface thermal transients are compared.