They twice broke the world record fee in order to sign Ronaldo and Christian Veri. Though they wanted to sign the best players in the world, they would often sell their players too early and later regret it. Though they do have an impressive 18 Serie A titles, 3 European clubs and they can also proudly say that they are the very few and the only Italian team who has won the treble. But their last trophy was the Coppa Italia in 2011.
The more painful thing to watch for Inter Milan fans is not only the demise of the giants but how their rivals Juventus, over the time, have performed domestically as well as in the transfer market, signing players like Paul Pogba, Sami Khedira, Andrea Pirlo and Dani Alves for free and they have won Scudetto six times in a row.
The players which Inter Milan have sold are not even the players they were forced to sell, but players happy to let go.
Here we look at 6 players Inter Milan sold to early.
#6 Philippe Coutinho
Philippe Coutinho joined Inter Milan from Vasco Da Gama when he was just 18. Inter Milan chairman Massimo Moratti hailed him as the future of Inter Milan. Despite that, he failed to land down a regular spot in the Inter Milan starting line up.
In his first season, he made 20 appearances and only 6 appearances came after Rafa Benitez left the club. He made further 8 appearances in the second half of the 2011-12 season and he was loaned to Espanyol for the second half of the season.
At Espanyol, he had his most productive spell in his career before Liverpool. In 16 appearances for the La Liga side, he scored 5 goals and registered 1 assist.
He returned to Inter for the 2012-13 campaign and made 19 appearances for the Italian giants. Then in the winter transfer window, Liverpool signed the Brazilian for £8.5m. It was revealed that Rafa Benitez played a key role in the deal.
Fast forward 3 years and Coutinho at the age of 25 is one of the best players in the world and many view him as a successor to Barcelona legend Andrés Iniesta.
Coutinho also played a crucial part in Liverpool's title challenge in 2013-14 under Brendan Rodgers and after the appointment of Jurgen Klopp, he has taken his game to a whole new level. Recently he was a Ballon d'Or nominee as well and no Inter Milan player has even managed to be a Ballon d'Or nominee since Diego Forlan in 2011.
It is very much clear that Inter Milan regret selling him, they would have had a world-class player if they did not sell him and how exciting it would have been to watch him link up with current Inter Milan captain Mauro Icardi.
#5 Leonardo Bonucci
Leonardo Bonucci spent two years at Inter Milan where he managed to make just one appearance for the club and he was sold to Treviso. Since the departure of Lucio and Samuel from Inter Milan, they have struggled for a solid defensive figure at the back before the arrival of Miranda from Atletico Madrid.
At the age of 30, Bonucci is one of the best defenders in the world and what is worse is the fact that Inter Milan arch-rivals Juventus and AC Milan have enjoyed the services of Italian international.
Since the time he left Inter Milan he has enjoyed plenty of success winning the Serie A six times, 3 Coppa Italia titles, 3 Italian Super Cups and he twice came very close to winning the Champions League only to be beaten by Barcelona and Real Madrid in the final.
You can't really presume that Bonucci would have become a top player at Inter, but they should have trusted the younger players more considering their old guard needed replacing. But they instead allowed him to leave for cheap, unlike Juventus who made a good profit from selling him to AC Milan.
#4 Andrea Pirlo
Inter Milan allowed Pirlo to leave after 40 games for them. He joined their cross-town rivals AC Milan in 2001. What Inter did not realise was that they were not selling a youngster, but a player who would later become one of the best deep-lying midfielders of the modern football.
Pirlo went on to become one of the best midfielders of his generation winning six Serie A and two Champions Leauge with AC Milan and Juventus.
His vision and passing made him stand out. He orchestrated attacks from deep with outrageous long passes that reached its target with incredible precision. Not only was he known for his playmaking skills from deep, but he was also described as a silent leader who would do the talking with his feet.
His cool and calm attitude was also very rare as he once quoted, "I don't feel pressure ... I don't give a toss about it. I spent the afternoon of Sunday, 9 July 2006 in Berlin sleeping and playing the PlayStation. In the evening, I went out and won the World Cup."
Inter Milan had a decent midfield duo in Dejan Stankovi? and Esteban Cambiasso. The addition of Pirlo would have undoubtedly made them stronger.
The only condolences Inter Milan can have is the fact that their rivals AC Milan made the same mistake and allowed Pirlo to join Juventus for free and he went to win 4 more Serie A titles with the Old Lady.
#3 Roberto Carlos
Roberto Carlos will always be remembered as the player who scored the most astonishing free kick you'll ever see. But the skills and trickery were not enough to keep him at the San Siro.
He spent one season at Inter Milan, before being sold to Real Madrid. The Nerazzurri signed him from Palmeiras in 1995 and by that time he was already a Brazilian international.
The former Fenerbahce fullback later revealed that his disastrous one season at the San Siro was down to the differences between him and the then manager of Inter Milan Roy Hodgson. The left-back made 30 appearances for the club that season as Inter finished seventh in the Serie A that season. Inter were unsure that whether he is a fullback or a winger.
Carlos also revealed that Roy Hodgson wanted to play him in the midfield and there was a chance that it would have ruined his career. He went to say that Inter lost the Uefa Cup final against Schalke because of him and he doesn't know much about football.
Real Madrid lured the then Brazilian international to the Bernabeu where he established himself as one of the best left-backs of his generation. At Real Madrid, he won the 4 La Liga titles and 3 Champions League titles.
#2 Clarence Seedorf
It looks like Inter Milan did not learn any lesson after selling Pirlo to AC Milan. Soon after Andrea Pirlo left the club, a year later Inter Milan made another blunder and allowed another generation-defining midfielder leave the club. This time, in the form of Clarence Seedorf.
The Dutch international arrived at Inter Milan for $24.35 million from Real Madrid, having already won the Champions Leauge twice with Ajax and Madrid. Seedorf joined AC Milan in a swap deal, which saw Francesco Coco move in other direction.
Coco managed only 26 appearances for Inter Milan over the course of five seasons and Seedorf made 300 appearances for the AC Milan winning two Scudettos and two Champions League titles.
What a midfield it would have been had Inter kept both Pirlo and Seedorf, two generation-defining midfielders.
#1 Dennis Bergkamp
Dennis Bergkamp is the name every Arsenal fan would rave about. But for the Inter fans, he is another talented player who was allowed to leave for cheap for Maurizio Ganz. In other words, another player they regret selling so early.
The Dutch international arrived at the San Siro from Ajax in 1993. There were high expectations from the fans after he had finished second in the Ballon d'Or standing that year.
Inter spent $7.3m on the Ajax attacker and he was showing signs of promise as he scored 30 goals in 81 appearances for the Nerazzurri. However, Inter Milan's new owner, Massimo Moratti, preferred new signing Maurizio Ganz and Dennis Bergkamp was allowed to leave for Arsenal.
Bergkamp was reaching the peak of his potential at the time when Inter Milan allowed him to leave. Eleven seasons later in 2006, he retired and his goal against Newcastle was voted as the best goal of the Premier League Era.
The former Dutch International was cast in bronze alongside a few other legends outside Emirates. During his time at Arsenal, he won seven major trophies and he was also a crucial part of the Arsenal famous invincibles, who went on to stay unbeaten for a season.
He could have been an Inter Milan legend if had they given him the chance to shine.