Fiber mounting units for supporting an optical fiber for fiber laser systems are disclosed and include a base body having a fiber end attachment section, a fiber guide section, and a connection section arranged between the fiber end attachment section and the fiber guide section. The fiber end attachment section is adapted to attach a receiving element, which holds a fiber end portion of the optical fiber, the fiber guide section is adapted to guide a fiber central portion of the optical fiber, and the connection section is configured as a flexure bearing between the fiber end attachment section and the fiber guide section.