  The H.E.S.S. Imaging Air Cherenkov Telescope system is very well suited to
perform follow-up observations of detections at other wavelengths or messengers
due to its fast reaction and its comparably low energy threshold. These
advantages are fully exploited via a largely automatized system reacting to
alerts from various partner observatories covering all wavelengths and
astrophysical messengers. In this contribution we provide an overview and
recent results from H.E.S.S. programs to follow up on multi-wavelength and
multi-messenger alerts. We present ToO observations searching for high-energy
gamma-ray emission in coincidence with electromagnetic transients Fast Radio
Bursts as well as multi-messenger transients related to high-energy neutrinos
and Gravitational Waves.
