A neutrino burst was observed by the Kamiokande II detector on 23 February 1987, at 7:35:35 UT, consisting of 11 electron events with energies between 7.5 and 36 MeV. The first two events were traced back to the Large Magellanic Cloud, with angles of 18°±18° and 15°±27°. This observation followed the optical detection of the supernova SN1987A on 24 February 1987. The Kamiokande II detector, designed for nucleon decay and solar neutrino detection, detected these events, confirming the neutrino burst from SN1987A. The burst was analyzed and found to be consistent with a uniform volume distribution. The events were identified as neutrinos from SN1987A, with an estimated integral flux of 1.0×10¹⁰ ν̄ₑ cm⁻² and a neutrino output of 8×10⁵² ergs. This observation was the first direct detection of a neutrino burst from a supernova, aligning with current models of supernova collapse and neutron-star formation. The results have significant implications for particle physics, particularly regarding neutrino lifetimes and mass. The study was supported by various institutions and acknowledged the cooperation of the Kamioka Mining and Smelting Company. No other neutrino bursts were found in the data, and the observed events were confirmed to be genuine, not due to background processes. The findings provide crucial evidence for the neutrino emission from SN1987A and support the theoretical models of supernova physics.A neutrino burst was observed by the Kamiokande II detector on 23 February 1987, at 7:35:35 UT, consisting of 11 electron events with energies between 7.5 and 36 MeV. The first two events were traced back to the Large Magellanic Cloud, with angles of 18°±18° and 15°±27°. This observation followed the optical detection of the supernova SN1987A on 24 February 1987. The Kamiokande II detector, designed for nucleon decay and solar neutrino detection, detected these events, confirming the neutrino burst from SN1987A. The burst was analyzed and found to be consistent with a uniform volume distribution. The events were identified as neutrinos from SN1987A, with an estimated integral flux of 1.0×10¹⁰ ν̄ₑ cm⁻² and a neutrino output of 8×10⁵² ergs. This observation was the first direct detection of a neutrino burst from a supernova, aligning with current models of supernova collapse and neutron-star formation. The results have significant implications for particle physics, particularly regarding neutrino lifetimes and mass. The study was supported by various institutions and acknowledged the cooperation of the Kamioka Mining and Smelting Company. No other neutrino bursts were found in the data, and the observed events were confirmed to be genuine, not due to background processes. The findings provide crucial evidence for the neutrino emission from SN1987A and support the theoretical models of supernova physics.