Abstract: With the increasing adoption of hydrogen energy, the demand for hydrogen sensing has grown accordingly. Due to its inherent advantages, including intrinsic safety, immunity to electromagnetic interference, compact size, and capability of multiplexing, fiber-optic hydrogen sensors have become as a prominent approach in this field. This review provides the recent advances in fiber optic hydrogen sensors, including various types of sensing mechanisms, including fiber grating, micro-mirror, interferometric, evanescent field, and surface plasmon resonance-based fiber optic hydrogen sensors, along with a detailed comparison of their sensing performances. By incorporating advanced materials and the corresponding fabrication techniques, fiber optic hydrogen sensors can achieve sensitive hydrogen detection at the 10⁻⁶ level and with rapid response at the sub-second level. With the implementation of the hydrogen energy strategy, fiber-optic hydrogen sensors are expected to see broader adoption in various scenarios, including production, storage and transportation, as well as applications of hydrogen energy.