Explore the cutting-edge developments in high-energy neutrino astronomy through this keynote plenary session presented by Marcos Santander at the APS April Meeting 2019. Delve into the fascinating world of cosmic messengers, focusing on neutrinos and their ability to traverse vast cosmic distances unimpeded. Examine the detection principles of gigaton-scale detectors and learn about the current generation of neutrino observatories. Discover the significance of the 2013 IceCube discovery of an astrophysical neutrino flux and the 2017 identification of a blazar as a potential neutrino source. Investigate various neutrino sources, including the galactic plane and gamma-ray bursts, and explore future prospects in neutrino astronomy. Gain insights into ongoing and planned neutrino detection efforts at Lake Baikal, the Mediterranean Sea, and the South Pole, concluding with an overview of the neutrino flux and its implications for our understanding of the universe.