Both of the clubs have shared the 80,000 capacity ground since 1947 and it's hosted numerous World Cup matches and European Cup finals over the past decades.
But soon, work will begin to bring the stadium into the 21st century, with hopes it will be ready for the 2022/23 season.
So far, very little is known about what the new venue will look like, but it is believed the capacity will be reduced to around 60,000.
Detailed plans were actually due to be unveiled on Thursday morning, but ahead of the official announcement, a video has been leaked online which appears to show the expected designs.
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According to the Daily Mail, American company Populous are believed to be front-runners to win the contract and their stadium design is inspired by the historic Duomo di Milano church.
The outside of the ground will feature a glass shell, while the surrounding areas will also be transformed to create what Populous describes as 'the most sustainable sports precinct in Europe'.
Although the original leaked video has been removed, a shorter version has been re-uploaded to YouTube, which you can view below. Screenshots are also included below.
It's fair to say these San Siro designs are absolutely stunning.
The Milan stadium may be one of the world's most famous, but it's hard to argue with the decision to modernise it, especially given these plans.
Natural ventilation systems, a rainwater harvesting roof and dedicated green spaces around the ground will all help the two Milan clubs protect their natural environment - and that's got to be a good thing.
We can expect to hear more details on the new San Siro once the full plans are released on Thursday morning.News Now - Sport News