For the time period from 1.5 to 4 Myr before the present we found in deep ocean ferromanganese crusts a 53Mn excess concentration in terms of 53 Mn / Mn of about 4 × 10−14 over that expected for cosmogenic production. We conclude that this 53Mn is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where 60Fe has been found earlier. This overabundance confirms the supernova origin of that 60Fe. For the first time, supernova-formed 53Mn has been detected and it is the second positively identified radioisotope from the same supernova. The ratio 53Mn / 60 Fe of about 14 is consistent with that expected for a SN with a 11–25     M ⊙ progenitor mass and solar metallicity.