Mandzukic was a free agent after ending his contract with Qatari side Al Duhail in July last year.
The 34-year-old comes with a wealth of experience to aid AC Milan’s push for a first Serie A title since the 2010/2011 season.
Mandzukic won four Serie A titles with Juventus between 2015 and 2019, and also won the UEFA Champions League and two Bundesliga trophies with Bayern Munich.
An official statement announcing Mandzukic’s arrival at the San Siro read: “AC Milan is delighted to announce the signing of Mario Mandžukić. The Club and the striker have agreed on a deal until the end of the current season with an option to extend the contract for the next one.
“Born in Slavonski Brod (Croatia) on May 21, 1986, Mario Mandžukić started his professional career in 2004 with NK Marsonia before joining NK Zagreb and GNK Dinamo Zagreb.
“In Summer 2010, he moved to Germany to play for VfL Wolfsburg (60 appearances and 20 goals) and Bayern Munich (88 appearances and 48 goals).
“In the 2014/15 season, he went on to play for Atletico Madrid scoring 20 goals in 43 appearances before joining FC Juventus. In his five seasons with FC Juventus, he made 162 appearances and scored 44 goals.
“In January 2020, he joined Qatari side Al-Duhail with one goal in 7 appearances.
“Mandžukić has won 24 trophies including 1 UCL, 1 UEFA Super Cup, 1 FIFA Cup World Cup, 9 championships and 12 between national Cups and Super Cups. He is the second-best scorer ever of the Croatian national team with 33 goals in 89 appearances.”
Stefano Pioli’s men are currently three points clear at the top of the table after beating Cagliari 2-0 on Monday.
Mandzukic was a member of the Croatia side that made it to the final of the FIFA World Cup in 2018, scoring three goals in Russia.
He scored two goals in the final, including an own goal as Croatia lost 4-2 to France.