Watch a dramatic encounter with two red cards and six goals, including a spectacular Ismael Bennacer volley and Zlatan Ibrahimovic scoring at both ends.
It was certainly not dull at the Stadio Dall’Ara, as Milan raced into a 2-0 lead with Rafael Leao’s deflected strike and a Davide Calabria rocket.
Adama Soumaoro saw red for a last man foul on Rade Krunic, but Bologna scored twice in three minutes for 2-2 with Musa Barrow and an Ibrahimovic own goal.
Roberto Soriano was also dismissed for a very high and dangerous tackle on Fode Ballo-Toure.
Both sides threatened to score more, but Bennacer broke through with a magical volley from the edge of the area.
Ibrahimovic sealed the 4-2 scoreline in stoppages, aged 40 years and 20 days.