Antiferroelectric materials, where the transition between antipolar and polar phase is controlled by external electric fields, offer exceptional energy storage capacity with high efficiencies, giant electrocaloric effect, and superb electromechanical response. PbZrO3 is the first discovered and the archetypal antiferroelectric material. Nonetheless, substantial challenges in processing phase pure PbZrO3 have limited studies of the undoped composition, hindering understanding of the phase transitions in this material or unraveling the controversial origins of a low‐field ferroelectric phase observed in lead zirconate thin films. Leveraging highly oriented PbZrO3 thin films, a room‐temperature ferrielectric phase is observed in the absence of external electric fields, with modulations of amplitude and direction of the spontaneous polarization and large anisotropy for critical electric fields required for phase transition. The ferrielectric state observations are qualitatively consistent with theoretical predictions, and correlate with very high dielectric tunability, and ultrahigh strains (up to 1.1%). This work suggests a need for re‐evaluation of the fundamental science of antiferroelectricity in this archetypal material.