We report what we believe to be the first millijoule-class ytterbium-doped fiber laser system operating on the zero-phonon line at $977\mathrm{nm}$ . An actively Q-switched master fiber oscillator delivers nanosecond pulses (FWHM $12–32\mathrm{ns}$ ) at adjustable multiples of $10\mathrm{kHz}$ repetition rates that are further amplified in an ultralarge core photonic crystal fiber amplifier. At the highest available pumping level, a maximal average power of $78\mathrm{W}$ was obtained for $32\mathrm{ns}$ pulses at a repetition rate of $190\mathrm{kHz}$ , whereas the millijoule energy level was reached for $12\mathrm{ns}$ pulses at the lower repetition rate of $10\mathrm{kHz}$ .