Piezoelectric polymer (poled polyvinylidene fluoride), a Japanese development recently introduced into high fidelity technology, shows promise as a hydrophone material because of its flexibility, ruggedness, low density, and potentially low cost. A family of lightweight flexural disk hydrophones which use piezoelectric polymer are described. Measurements on a 3.8‐cm‐diam unit gave a sensitivity of −199 dBre1 V/μPa with good stability over ranges of 2 Hz–1 kHz, 0°–22°C, and 0–4 MPa static pressure. This particular unit uses two air‐backed flexural disks with a stack of four pieces of 30‐μm polymer film glued to each disk, resulting in a combined capacitance of 1 nFd. This hydrophone has a mass of 24 g in air and is neutrally buoyant in water. A theoretical analysis which shows the variation of hydrophone performace as a function of design parameters is presented, and the material properties of piezoelectric polymer and piezoelectric ceramic are compared. [Work supported by NAVSEA and NAVELEX.]