We present breakthrough pulse energy performance (up to 300 μJ) from monolithic fiber-optic femtosecond laser systems that are developed for industrial materials processing. Whereas previous chirped pulse amplification (CPA) systems have implemented fiber-optic gain elements within free-space oscillator-amplifier circuits [1-3], we present monolithic fiber-optic CPA systems — where the mode-locked oscillator, pulse stretcher, pulse shaper, pulse picker, and all amplifier stages are comprised of fusion spliced fiber devices — emitting up to 300 μJ compressed pulse output with duration <500 fs (FWHM). This is a 6 times higher pulse energy than previously reported for monolithic fiber femtosecond lasers [4,5]. Higher femtosecond pulse energy enables cutting and drilling through thicker materials, at faster rates, without imposing a heat affected zone (HAZ). Generating this femtosecond beam with a monolithic fiber-optic system provides the most compact and stable form factor, suitable for industrial work cell integration and global factory deployment.