Australian wildfires burning from December 2019 to January 2020 injected approximately 0.9 Tg of smoke into the stratosphere; this is the largest amount observed in the satellite era. A comparison of numerical simulations to satellite observations of the plume rise suggests that the smoke mass contained 2.5% black carbon. Model calculations project a 1 K warming in the stratosphere of the Southern Hemisphere midlatitudes for more than 6 months following the injection of black‐carbon containing smoke. The 2020 average global mean clear sky effective radiative forcing at top of atmosphere is estimated to be −0.03 W m−2 with a surface value of −0.32 W m−2. Assuming that smoke particles coat with sulfuric acid in the stratosphere and have similar heterogeneous reaction rates as sulfate aerosol, we estimate a smoke‐induced chemical decrease in total column ozone of 10–20 Dobson units from August to December in mid‐high southern latitudes. Plain Language Summary: The 2019–2020 Australian bushfires injected a large amount of smoke that rose well into the stratosphere due to absorption of solar energy. A climate model is used to simulate the plume rise, transport, chemical, and climate impacts of the smoke from these massive bushfires. Simulations suggest that the smoke remained in the stratosphere for all of 2020 and that it measurably warmed the stratosphere by about 1–2 K for more than 6 months. The smoke particles were transported to high latitudes in the Southern Hemisphere and assuming similar heterogeneous reaction rates as sulfate aerosol should have produced about 4%–6% loss of the total column at high southern latitudes. Key Points: The 2019–2020 Australian wildfire injected about 0.9 Tg smoke containing 2.5% black carbon into the stratosphereClimate model simulations indicate that the smoke warmed the Southern Hemisphere stratosphere by 1 K for more than 6 monthsModel calculations estimate a decrease in ozone of 10–20 Dobson units from August to December at mid‐high southern latitudes [ABSTRACT FROM AUTHOR]