LAUSR

The development of ultrathin, stable ferroelectric materials is crucial for advancing high‐density, low‐power electronic devices. Nonetheless, ultrathin ferroelectric materials are rare due to the critical size effect. Here, a novel ferroelectric material, magnesium molybdenum oxide (Mg2Mo3O8) is presented. High‐quality ultrathin Mg2Mo3O8 crystals are synthesized using chemical vapor deposition (CVD). Ultrathin Mg2Mo3O8 has a wide bandgap (≈4.4 eV) and nonlinear optical response. Mg2Mo3O8 crystals of varying thicknesses exhibit out‐of‐plane ferroelectric properties at room temperature, with ferroelectricity retained even at a 2 nm thickness. The Mg2Mo3O8 exhibits a relatively large remanent polarization ranging from 33 to 52 µC cm−2, which is tunable by changing its thickness. Notably, Mg2Mo3O8 possesses a high Curie temperature (>980 °C) across various thicknesses. Moreover, the as‐grown Mg2Mo3O8 crystals display remarkable stability under harsh environments. This work introduces nolanites‐type crystal into ultrathin ferroelectrics. The scalable synthesis of stable ultrathin ferroelectric Mg2Mo3O8 expands the scope of ferroelectric materials and may prosper applications of ferroelectrics.