In this Letter, we present the application of the inverted Hartmann mask for time-resolved single-shot phase-contrast x-ray imaging. The inverted Hartmann mask is a periodic array of free-standing gold pillars. The array is manufactured by UV lithography and electroplating. Time-resolved measurements are performed for imaging of pulsed laser ablation in liquids using white-beam synchrotron radiation. The inverted Hartmann mask in combination with a single-shot imaging technique provides sufficient differential phase contrast even at very short exposure times. It can be effectively used for phase-contrast x-ray imaging of fast dynamic processes with temporal resolution on the millisecond scale.