A fiber Bragg grating hydrophone includes a fluid chamber (1) and an optical fiber (2) in which a Bragg grating (3) is integrated, the optical fiber extending through the fluid chamber such that the Bragg grating is positioned inside the latter. The fluid chamber is filled with a compressible fluid and is defined by a rigid casing (4) including two end surfaces (28a, 28b) that are rigidly connected to the optical fiber. At least one of the two end surfaces of the rigid casing includes an opening (5a, 5b) closed by a deformable diaphragm (6a, 6b) that is rigidly connected to the optical fiber and that can be deformed in reaction to a difference in the pressures applied to the surfaces thereof, thereby modifying the length of the optical fiber as measured by a variation in the wavelength of a luminous flux extracted from the optical fiber.