The existence of abundant post-starburst and quiescent galaxies just about 1–2 Gyr after the Big Bang challenges our current model of galaxy evolution1–3. Cosmological simulations suggest that quasar feedback is likely the most promising mechanism responsible for this rapid quenching4–6. Here we report a high detection rate (6/27) of exceptionally fast and powerful galaxy-scale outflows traced by [O iii] emission in z ≈ 5–6 luminous quasars as shown by the James Webb Space Telescope, with velocity up to about 8,400 km s−1 and order-of-magnitude kinetic energy outflow rates up to around 260% of the observed quasar bolometric luminosities. This fraction is >3.9 and 8.8 times that in comparison samples at z ≈ 1.5–3.5 and z < 1, respectively. These extreme outflows are comparable to or even faster than the most rapid [O iii] outflows reported at z ≲ 3, and could reach the circumgalactic medium or even the intergalactic medium. The average kinetic energy outflow rate of our sample is more than 2 dex higher than that of the lower-redshift comparison samples. The substantially higher frequency of outflows with energetics well above the threshold for negative feedback in our sample strongly suggests that quasar feedback plays an important part in efficiently quenching and regulating early massive galaxies.
