High-energy neutrinos provide a unique probe of the most extreme nonthermal processes in the Universe. The detection of the ultra-high-energy neutrino event KM3-230213A by the KM3NeT neutrino telescope, with an inferred parent-neutrino energy of O(1017 eV), represents a major step forward in neutrino astronomy. In this review, we summarize the main properties of the event and discuss its interpretation within different astrophysical and cosmological scenarios, including active galactic nuclei, transient sources, and cosmogenic neutrinos, highlighting the role of multimessenger constraints. Despite extensive follow-up observations, no unambiguous electromagnetic counterpart has been identified, and the event remains in tension with the absence of comparable detections in other experiments. This situation leaves open the possibility of more complex source scenarios or contributions from physics beyond the Standard Model. We also discuss the implications for the ultra-high-energy neutrino landscape and the prospects for future observations with next-generation detectors. KM3-230213A provides a unique opportunity to probe particle acceleration and neutrino production at energies far beyond the reach of terrestrial experiments.
- Open Access
- Review
KM3-230213A: The Highest-Energy Cosmic Neutrino
Author Information
Received: 27 May 2026 | Revised: 29 Jul 2026 | Accepted: 01 Sep 2026 | Published: 04 Sep 2026
Abstract
Keywords
ultra-high-energy neutrinos | KM3-230213A | neutrino astronomy | multimessenger astrophysics | KM3NeT
References
- 1.
Halzen, F. High-energy neutrino astrophysics. Nat. Phys. 2017, 13, 232–238.
- 2.
The IceCube Collaboration. Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector. Science 2013, 342, 1242856.
- 3.
Aartsen, M.G.; Abbasi, R.; Abdou, Y.; et al. First Observation of PeV-Energy Neutrinos with IceCube. Phys. Rev. Lett. 2013, 111, 021103.
- 4.
Aartsen, M.; Ackermann, M.; Adams, J.; et al. Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert. Science 2018, 361, 147–151.
- 5.
Abbasi, R.; Ackermann, M.; Adams, J.; et al. Evidence for neutrino emission from the nearby active galaxy NGC 1068. Science 2022, 378, 538–543.
- 6.
Adrian-Martınez, S.; Ageron, M.; Aharonian, F.; et al. Letter of intent for KM3NeT 2.0. J. Phys. G Nucl. Part. Phys. 2016, 43, 084001.
- 7.
The KM3NeT Collaboration. Observation of an ultra-high-energy cosmic neutrino with KM3NeT. Nature 2025, 638, 376–382.
- 8.
The IceCube Collaboration. Detection of a particle shower at the Glashow resonance with IceCube. Nature 2021, 591, 220–224.
- 9.
KM3NeT Collaboration. Ultrahigh-Energy Event KM3-230213A within the Global Neutrino Landscape. Phys. Rev. X 2025, 15, 031016.
- 10.
Das, S.; Zhang, B.; Razzaque, S.; et al. Cosmic-Ray Constraints on the Flux of Ultra-High-Energy Neutrino Event KM3-230213A. Astrophys. J. 2025, 991, 96.
- 11.
The Telescope Array Collaboration. An extremely energetic cosmic ray observed by a surface detector array. Science 2023, 382, 903–907.
- 12.
Mooney, C. Probing for Gamma-Ray Emission near KM3-230213A Neutrino Event with VERITAS. In Proceedings of the 39th International Cosmic Ray Conference, Geneva, Switzerland, 15–24 July 2025; p. 953.
- 13.
Crnogorcevic, M.; Blanco, C.; Linden, T. Looking for the gamma-Ray cascades of the KM3-230213A neutrino source. J. Cosmol. Astropart. Phys. 2025, 10, 009.
- 14.
Filipovic, M.D.; Smeaton, Z.J.; Bradley, A.C.; et al. ASKAP and VLASS Search for a Radio-continuum Counterpart of Ultra-high-energy Neutrino Event KM3–230213A. Astrophys. J. Lett. 2025, 984, L52.
- 15.
Adriani, O.; Aiello, S.; Albert, A.; et al. On the Potential Galactic Origin of the Ultra-High-Energy Event KM3-230213A. Astrophys. J. 2026, 1003, 157.
- 16.
Murase, K.; Inoue, Y.; Dermer, C.D. Diffuse Neutrino Intensity from the Inner Jets of Active Galactic Nuclei: Impacts of External Photon Fields and the Blazar Sequence. Phys. Rev. D 2014, 90, 023007.
- 17.
Adriani, O.; Aiello, S.; Albert, A.; et al. Characterizing Candidate Blazar Counterparts of the Ultra-High-Energy Event KM3-230213A. Astron. J. 2026, 172, 139.
- 18.
Adriani, O.; Albert, A.; Alhebsi, A.R.; et al. Blazars as a potential origin of the KM3-230213A event. J. Cosmol. Astropart. Phys. 2026, 03, 033.
- 19.
Dzhatdoev, T. The blazar PKS 0605-085 as the origin of the KM3-230213A neutrino event. In Proceedings of the 39th International Cosmic Ray Conference, Geneva, Switzerland, 15–24 July 2025; p. 1032.
- 20.
Yuan, C.; Pfeiffer, L.;Winter,W. An Accretion Flare Interpretation for the Ultra-High-Energy Neutrino Event KM3-230213A. Astrophys. J. Lett. 2026, 998, L1.
- 21.
Kivokurtseva, P.; Troitsky, S. Can a gamma-ray dim radio blazar produce a 200-PeV neutrino? The case of PMN J0606-0724 and KM3-230213A. arXiv 2025, arXiv:2509.10352.
- 22.
Fichet de Clairfontaine, G.; Perucho, M.; Martı, J.M. Jet–red giant interactions as a source of extragalactic neutrinos: Insights from KM3–230213A. Mon. Not. R. Astron. Soc. 2025, 544, 4217–4225.
- 23.
Waxman, E.; Bahcall, J. High Energy Neutrinos from Cosmological Gamma-Ray Burst Fireballs. Phys. Rev. Lett. 1997, 78, 2292–2295.
- 24.
Meszaros, P. Gamma-ray bursts. Rep. Prog. Phys. 2006, 69, 2259–2321.
- 25.
Adriani, O.; Albert, A.; Alhebsi, A.R.; et al. Constraining gamma-ray burst parameters with the first ultra-high energy neutrino event KM3-230213A. Astron. Astrophys. 2026, 710, A168.
- 26.
Neronov, A.; Oikonomou, F.; Semikoz, D. KM3-230213A: An ultrahigh energy neutrino from a year-long astrophysical transient Phys. Rev. D 2026, 113, 083024.
- 27.
Yu, S.; Zhang, B.T. A Unified Framework for 10 TeV to EeV Diffuse Neutrino Sky and KM3-230213A. Astrophys. J. Lett. 2026, 1002, L45.
- 28.
Mukhopadhyay, M.; Kimura, S.S. High energy neutrinos from pulsar-powered optical transients: LFBOTs as potential origin of the KM3NeT event KM3-230213A. arXiv 2026, arXiv:2601.22266.
- 29.
Berezinsky, V.S.; Zatsepin, G.T. Cosmic rays at ultra high energies (neutrino?). Phys. Lett. B 1969, 28, 423–424.
- 30.
Anchordoqui, L.A. Ultra-high-energy cosmic rays. Phys. Rep. 2019, 801, 1–93.
- 31.
Adriani, O.; Aiello, S.; Albert, A.; et al. On the Potential Cosmogenic Origin of the Ultra-high-energy Event KM3-230213A. Astrophys. J. Lett. 2025, 984, L41.
- 32.
Kuznetsov, M.Y.; Petrov, N.A.; Savchenko, Y.S. Ultra-High Energy Event KM3-230213A as a Cosmogenic Neutrino in Light of Minimal UHECR Flux Models. JETP Lett. 2026, 123, 287–297.
- 33.
Alhebsi, A.R.; van Vliet, A.; Ehlert, D.; et al. Implications of a Cosmogenic Origin of KM3-230213A for Ultra-High-Energy Protons. Astrophys. J. 2026, 1003, 235.
- 34.
Zhang, Q.; Huang, T.-Q.; Li, Z. Cosmogenic Neutrino Point Source and KM3-230213A. Astrophys. J. 2025, 990, 78.
- 35.
Boxi, S.; Das, S.; Gupta, N. Cosmogenic Origin of KM3-230213A: Delayed Gamma-Ray Emission from A Cosmic-Ray Transient. Astrophys. J. Lett. 2026, 997, L3.
- 36.
Cermenati, A.; Ambrosone, A.; Aloisio, R.; et al. Scrutinizing the cosmogenic origin of the KM3-230213A event: A multi-messenger Perspective. arXiv 2025, arXiv:2507.11993.
- 37.
Bhattacharjee, P.; Sigl, G. Origin of ultra-high-energy cosmic rays. Phys. Rep. 2000, 327, 109–247.
- 38.
Feng, J.L. Dark Matter Candidates from Particle Physics and Methods of Detection. Annu. Rev. Astron. Astrophys. 2010, 48, 495–545.
- 39.
The KM3NeT Collaboration. KM3NeT Constraint on Lorentz-Violating Superluminal Neutrino Velocity Commun. Phys. 2025, 8, 457.
- 40.
Satunin, P. Ultra-high-energy event KM3-230213A constraints on Lorentz Invariance Violation in neutrino sector. Eur. Phys. J. C 2025, 85, 545.
- 41.
Yang, Y.-M.; Lv, X.-J.; Bi, X.-J.; et al. Constraints on Lorentz-invariance violation in the neutrino sector from the ultrahigh-energy event KM3-230213A. Phys. Rev. D 2025, 111, 123037.
- 42.
Carmona, J.M.; Cortes, J.L.; Reyes, M.A. Superluminal constraints from ultra-high-energy neutrino events. J. Cosmol. Astropart. Phys. 2026, 03, 023.
- 43.
Amelino-Camelia, G.; D’Amico, G.; Fabiano, G. On testing in-vacuo dispersion with the most energetic neutrinos: KM3-230213A case study. Phys. Lett. B 2025, 868, 139764.
- 44.
Cattaneo, P.W. Constraints on Lorentz invariance from the event KM3-230213A. Eur. Phys. J. C 2025, 85, 529.
- 45.
Wang, R.; Zhu, J.; Li, H.; et al. Association of 220 PeV Neutrino KM3-230213A with Gamma-Ray Bursts. Res. Notes AAS 2025, 9, 65.
- 46.
Wang, R.; Ma, B.-Q. Correlation between Ultra-High-Energy Neutrino KM3-230213A and Gamma-Ray Bursts. arXiv 2026, arXiv:2604.13879.
- 47.
Brdar, V.; Chattopadhyay, D.S. Does the 220 PeV Event at KM3NeT Point to New Physics? Phys. Rev. Lett. 2026, 136, 081001.
- 48.
He, Y.; Liu, J.; Wang, X.-P.; et al. Implications of the KM3NeT ultrahigh-energy event on neutrino self-interactions. Phys. Rev. D 2026, 113, 043022.
- 49.
Petropavlova, M.; Smetana, A.; Trautner, A. Constraints on Neutrino Secret Interactions from Multi-messenger Neutrinos Scattering on CνB. arXiv 2025, arXiv:2505.14332.
- 50.
Bertolez-Martınez, T.; Herrera, G.; Martınez-Mirave, P.; et al. Highest-energy neutrino event constrains dark matter-neutrino interactions. Phys. Rev. D 2026, 113, 103052.
- 51.
Mondol, R.; Bouri, S.; Saha, A.K.; et al. Road through Darkνess: Probing dark matter-neutrino interactions using KM3-230213A. arXiv 2025, arXiv:2506.19910.
- 52.
Borah, D.; Das, N.; Okada, N.; et al. Possible origin of the KM3-230213A neutrino event from dark matter decay. Phys. Rev. D 2025, 111, 123022.
- 53.
Kohri, K.; Paul, P.K.; Sahu, N. Super heavy dark matter origin of the PeV neutrino event: KM3-230213A. Phys. Rev. D 2025, 112, L031703.
- 54.
Barman, B.; Das, A.; Sarmah, P. What KM3-230213A event may tell us about the neutrino mass and dark matter. Phys. Rev. D 2025, 112, 075014.
- 55.
Khan, S.; Kim, J.; Ko, P. Linking the KM3-230213A neutrino event to dark matter decay and gravitational wave signals. J. Cosmol. Astropart. Phys. 2025, 11, 033.
- 56.
Murase, K.; Narita, Y.; Yin, W. Superheavy dark matter from the natural inflation in light of the highest-energy astroparticle events. J. Cosmol. Astropart. Phys. 2025, 10, 109.
- 57.
Su, Y.-H.; Chen, S.-Y.; Cai, C.; et al. Interpreting the KM3-230213A PeV Neutrino Event via Vector Dark Matter Decay and Its Multi-Messenger Signatures. arXiv 2025, arXiv:2507.21534.
- 58.
Aloisio, R.; Ambrosone, A.; Evoli, C. Constraining superheavy dark matter with the KM3-230213A neutrino event. Phys. Rev. D 2026, 113, 043024.
- 59.
Boccia, A.; Iocco, F. Could the KM3–230213A event be caused by an evaporating primordial black hole? Phys. Rev. D 2025, 112, 063045.
- 60.
Anchordoqui, L.A.; Halzen, F.; Lust, D. Neutrinos from Primordial Black Holes in Theories with Extra Dimensions. Phys. Rev. D 2025, 112, 083034.
- 61.
Singh, P.; Dhuria, M.; Varghese Job, N. KM3-230213A and IceCube Neutrino Events from Metastable Dark Matter of Primordial Black Hole Origin. Phys. Rev. D 2026, 113, 103014.
- 62.
Aldecoa-Tamayo, I.; Byrnes, C.T.; Seery, D. Primordial black holes in Randall-Sundrum: Cosmological signatures. J. Cosmol. Astropart. Phys. 2026, 02, 002.
- 63.
Jiang, S.; Huang, F.P. Pseudo-Goldstone dark matter from primordial black holes: Gravitational wave signatures and implications for KM3-230213A event at KM3NeT. J. Cosmol. Astropart. Phys. 2025, 06, 023.
- 64.
Choi, K.-Y.; Lkhagvadorj, E.; Mahapatra, S. A possible cosmological origin of the KM3-230213A event. J. Cosmol. Astropart. Phys. 2025, 10, 079.
- 65.
Airoldi, L.F.T.; Alves, G.F.S.; Perez-Gonzalez, Y.F.; et al. Could a Primordial Black Hole Explosion Explain the extremely high-energy KM3NeT neutrino Event? Phys. Rev. Lett. 2026, 136, 041002.
- 66.
Narita, Y.; Yin, W. Explaining the KM3-230213A Detection without Gamma-Ray Emission: Cosmic-Ray Dark Radiation. J. Cosmol. Astropart. Phys. 2026, 05, 030.
- 67.
Farzan, Y.; Hostert, M. Astrophysical flux of dark particles as a solution to the KM3NeT and IceCube tension over KM3-230213A. J. High Energy Phys. 2025, 10, 208.
- 68.
Dev, P.S.B.; Dutta, B.; Karthikeyan, A.; et al. ‘Dark’ Matter Effect as a Novel Solution to the KM3-230213A Puzzle. arXiv 2025, arXiv:2505.22754.
- 69.
Arguelles, C.A.; Bertolez-Martınez, T.; Burgos-Mondejar, A.; et al. Seafloor Topography Enhances KM3NeT Sensitivity to ANITA-like Events. arXiv 2025, arXiv:2510.21929v1.
- 70.
Sakharov, A.S.; Konoplich, R.; Gogberashvili, M. Ultra High Energy Neutrino Event KM3-230213A as a Signal of Electroweak Vacuum Turbulence in Merging Black Hole Binaries. Phys. Rev. D 2025, 112, 083061.
- 71.
Fang, K.; Halzen, F.; Hooper, D. Cascaded Gamma-Ray Emission Associated with the KM3NeT Ultrahigh-energy Event KM3-230213A. Astrophys. J. Lett. 2025, 982, L16.
- 72.
Olinto, A.V.; Anchordoqui, L.A.; Cummings, A.; et al. Prospects for PBR detection of KM3-230213A-like events. In Proceedings of the 39th International Cosmic Ray Conference, Geneva, Switzerland, 15–24 July 2025; p. 980.
- 73.
Muzio, M.S. for the ARA Collaboration. First Array-Wide Search for Diffuse UHE Neutrinos with the Askaryan Radio Array. In Proceedings of the 39th International Cosmic Ray Conference, Geneva, Switzerland, 15–24 July 2025; p. 1126.
- 74.
IceCube-Gen2 Collaboration. IceCube-Gen2: The Window to the Extreme Universe. J. Phys. G Nucl. Part. Phys. 2021, 48, 060501.
- 75.
Aguilar, J.A.; Allison, P.; Beatty, J.J.; et al. Design and Sensitivity of the Radio Neutrino Observatory in Greenland (RNO-G). J. Instrum. 2021, 16, P03025.
- 76.
Alvarez-Muniz, J.; Alves Batista, R.; Balagopal, V.A.; et al. The Giant Radio Array for Neutrino Detection (GRAND): Science and Design. Sci. China Phys. Mech. Astron. 2020, 63, 219501.
- 77.
TAMBO Collaboration. Measuring the high-energy neutrino sky using the deep-valley neutrino observatory TAMBO. Nat. Astron. 2026, 10, 947–951.
- 78.
Otte, A.N. Studies of an air-shower imaging system for the detection of ultrahigh-energy neutrinos. Phys. Rev. D 2019, 99, 083012.
- 79.
Hymon, K.; Chen, A.; Tsai, M.-X.; et al. POLARIS: A Sparse Radial Neutrino Telescope Design for the Pacific Ocean. arXiv 2026, arXiv:2604.12521.
- 80.
de Oliveira, C.; de Souza, V. Recent advances on multi-messenger astrophysics: Centaurus A, GW 170817, and KM3-230213A. arXiv 2025, arXiv:2507.16392.
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