Rafael Leao's early goal proved the difference as Milan beat Sampdoria 1-0 at San Siro on Sunday to climb to the top of Serie A.
Saturday's 1-1 draw between Inter and Napoli provided Milan with the opportunity to leapfrog both sides and they did exactly that without ever being at their best against Samp.
Leao calmly converted inside eight minutes after being assisted by keeper Mike Maignan and that was enough for the hosts, who have now won three in a row in all competitions.
Milan are two points clear of third-place Napoli and one point better off than reigning champions Inter, who still have a game in hand to play.
Milan had collected just one point from their past two home matches but started brightly and took the lead early on through Leao's 10th goal of the campaign.
The Portugal international controlled a long pass from Maignan, drove away from Bartosz Bereszynski into the opposition box and coolly fired away from Wladimiro Falcone.
Falcone produced a fine one-handed save to keep out a powerful Junior Messias drive and the Milan midfielder flashed another attempt narrowly wide the other side of half-time.
Sampdoria had a brief moment on top but the big chances continued to fall Milan's way, with Olivier Giroud twice being denied by the visiting keeper from a volley and a header.
The visitors never truly looked like finding a leveller, though, with Stefano Pioli's side seeing out the job to climb to the summit.
What does it mean? Tight at the top
After following up a late 2-1 comeback win over Inter with a 4-0 Coppa Italia quarter-final victory against Lazio in midweek, this latest result caps a fine week for Milan.
The Rossoneri will end a gameweek top of Serie A for only the second time this season in what is by some distance the tightest title race in Europe's top five leagues.
As for relegation-threatened Sampdoria, this was their 67th Serie A defeat to Milan – only against Inter (70) have they lost more games in the competition.
Route-one Rossoneri
Leao profited from Maignan's quick thinking to release the ball early for Milan's early breakthrough goal.
Maignan is the eighth goalkeeper to assist a goal in Europe's top five leagues this term, and the first Milan shot-stopper to do so in Serie A since Dida against Ascoli in 2006.
Giroud awakening
Milan's in-form striker had scored braces in back-to-back matches heading into this contest but simply could not find a way past man-of-the-match Falcone.
Giroud had five shots in total with an expected goals (xG) return of 0.40 without finding the net, compared to one shot and one goal for Leao, who had an xG of 0.33.
What's next?
Milan travel to Serie A's bottom side Salernitana next Saturday, while Sampdoria host Empoli the same day.