Intense electromagnetic impulses induced by Jupiter's lightning have been recognised to produce both low-frequency dispersed whistler emissions and non-dispersed radio pulses. Here we report the discovery of electromagnetic pulses associated with Jovian lightning. Detected by the Juno Waves instrument during its polar perijove passes, the dispersed millisecond pulses called Jupiter dispersed pulses (JDPs) provide evidence of low density holes in Jupiter's ionosphere. 445 of these JDP emissions have been observed in snapshots of electric field waveforms. Assuming that the maximum delay occurs in the vicinity of the free space ordinary mode cutoff frequency, we estimate the characteristic plasma densities (5.1 to 250 cm ) and lengths (0.6 km to 1.3 × 10  km) of plasma irregularities along the line of propagation from lightning to Juno. These irregularities show a direct link to low plasma density holes with ≤250 cm in the nightside ionosphere.