We investigated the ultrafast energy relaxation of photoexcited minority electrons in highly doped p-GaAs by means of femtosecond time resolved luminescence (Δt<90 fs). Our experiments allow the first observation of the extremely fast cooling of minority electrons within the Γ-valley. The electron mean energy decreases within 150 fs from 150 meV down to less than 50 meV. The total energy loss rate reaches values higher than 10−7 W per electron, representing the highest energy loss rates of electrons observed to date in monocrystalline semiconductors. Ensemble Monte Carlo simulations show that the electron-hole scattering is responsible for these high energy loss rates.