AbstractAbundant chemical diversity and structural tunability make organic–inorganic hybrid perovskites (OIHPs) a rich ore for ferroelectrics. However, compared with their inorganic counterparts such as BaTiO₃, their ferroelectric key properties, including large spontaneous polarization (P_s), low coercive field (E_c), and strong second harmonic generation (SHG) response, have long been great challenges, which hinder their commercial applications. Here, a quasi-one-dimensional OIHP DMAGeI₃(DMA = Dimethylamine) is reported, with notable ferroelectric attributes at room temperature: a largeP_sof 24.14 μC/cm²(on a par with BaTiO₃), a lowE_cbelow 2.2 kV/cm, and the strongest SHG intensity in OIHP family (about 12 times of KH₂PO₄(KDP)). Revealed by the first-principles calculations, its largeP_soriginates from the synergistic effects of the stereochemically active 4s²lone pair of Ge²⁺and the ordering of organic cations, and its low kinetic energy barrier of small DMA cations results in a lowE_c. Our work brings the comprehensive ferroelectric performances of OIHPs to a comparable level with commercial inorganic ferroelectric perovskites.