IMB is an acronym for a neutrino observatory located under Lake Erie. It is run by a group of American institutions headed by the University of California at Irvine, the University of Michigan, and the Brookhaven National Laboratory (hence the acronym).

IMB consists of a roughly cubical tank about 20 meters on a side, full of water and surrounded by 2048 photomultiplier tubes. IMB detects neutrinos by picking up the Cerenkov radiation generated when a neutrino collides with either a proton or an electron (both of which are plentiful in water). IMB is thus able to estimate the direction of the neutrino by analysing the spatial arrangement of the tubes that detected radiation.

The efficiency of IMB is quite low: if 100 trillion neutrinos pass through the detector, on average only one will be detected.

IMB is famous for having detected 8 of the 10⁵⁸ neutrinos emitted by Supernova 1987a.