The dominant neutrino fluxes at Earth from different sources are reviewed and the grand unified neutrino spectrum ranging from meV to PeV energies is presented. For each energy band and source, both theoretical expectations and experimental data are discussed. This compact review serves as a reference to those interested in neutrino astronomy, fundamental particle physics, dark-matter detection, high-energy astrophysics, geophysics, and other related topics.

• Received 2 November 2019

DOI:https://doi.org/10.1103/RevModPhys.92.045006