Noncentrosymmetric Mott ground state in the breathing kagome lattice <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Nb</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>Cl</mml:mi> <mml:mn>8</mml:mn>

The breathing Kagome material ${\mathrm{Nb}}_{3}{\mathrm{Cl}}_{8}$ has recently been identified as a single-band Mott insulator and theoretically predicted to host coexisting ferroelectricity, magnetism, and ferrovalley---yet experimental verification of these predictions remains lacking. Here, through polarization- and temperature-dependent Raman and second harmonic generation measurements, we reveal that the low-temperature (LT) phase of this material retains ${C}_{3}$ rotational symmetry while breaking inversion symmetry. We propose that the structural phase transition at ${T}_{s}$ corresponds to a stacking-order transition: from centrosymmetric AB stacking to noncentrosymmetric AA/BB stacking, driven by enhanced interlayer electric dipole-dipole interactions. With an AA/BB stacking sequence, the LT phase exhibits net electric dipole moments oriented perpendicular to the kagome plane. Our findings provide directly experimental evidence for the existence of a noncentrosymmetric Mott ground state, thereby establishing a unique platform for investigating the interplay between inversion symmetry breaking and strong electron correlation.