We discuss here a lunar impact flash recorded during the total lunar eclipse that occurred on 2019 January 21, at 4 h 41 m 38.09 +/- 0.01 s UT. This is the first time ever that an impact flash is unambiguously recorded during a lunar eclipse and discussed in the scientific literature, and the first time that lunar impact flash observations in more than two wavelengths are reported. The impact event was observed by different instruments in the framework of the MIDAS survey. It was also spotted by casual observers that were taking images of the eclipse. The flash lasted 0.28 s and its peak luminosity in visible band was equivalent to the brightness of a magnitude 4.2 star. The projectile hit the Moon at the coordinates 29.2 +/- 0.3 degrees S, 67.5 +/- 0.4 degrees W. In this work we have investigated the most likely source of the projectile, and the diameter of the new crater generated by the collision has been calculated. In addition, the temperature of the lunar impact flash is derived from the multiwavelength observations. These indicate that the blackbody temperature of this flash was of about 5700 K.