The ferroelectric domain wall, serving as the boundary between separate data carriers based on domains, has attracted widespread interest due to its distinctive physical properties. Although the domain walls in ferroelectric materials are narrower than those in magnetic materials due to their higher lattice anisotropy, they still account for a considerable proportion in ultrathin films, reducing storage efficiency to some extent. Here, ultrathin antiphase ferroelectric boundaries (APFBs) are presented and validated their feasibility as ferroelectric domain walls. The naturally formed APFB shows a sharp and straight morphology, with the characteristic of interlocking between the antiphase boundary (APB) and conventional 180° domain wall. The calculations from the density functional theory demonstrate that the APFBs undergo a significant but localized change in electronic structure. They largely retain the characteristics that are consistent with those of conventional domain walls, such as enhanced conductivity, irregular oxygen vacancy trapping energy, and vacancy-tunable physical properties. Finally, as techniques for precisely controlling the nucleation of APB developing, configurations with out-of-plane APFBs used as dividers may provide a promising strategy for miniaturizing ferroelectric devices.