Piezoelectric sensors that can work under various conditions with superior performance are highly desirable with the arrival of the Internet of Things. For practical applications, a large piezoelectric voltage coefficient g and a high Curie temperature T-c are critical to the performance of piezoelectric sensors. Here, we report a two-dimensional perovskite ferroelectric (4-minotetrahydropyran)(2)PbBr4 [(ATHP)(2)PbBr4] with a saturated polarization of 5.6 mu C cm(-2), high T-c of 503 K [above that of BaTiO3 (BTO, 393 K)], and extremely large g(33) of 660.3 x 10(-3) V m N-1 [much beyond that of Pb(Zr,Ti)O-3 (PZT) ceramics (20 to 40 x 10(-3) V m N-1), more than 2 times higher than that of poly(vinylidene fluoride) (PVDF, about 286.7 x 10(-3) V m N-1)]. Combined with the advantages of molecular ferroelectrics, such as light weight, easy and environmentally friendly processing, and mechanical flexibility, (ATHP)(2)PbBr4 would be a competitive candidate for next-generation smart piezoelectric sensors in flexible devices, soft robotics, and biomedical devices.