It's a group which shares 15 Champions League titles between the four clubs.
The Champions League campaign will begin on the 14th of September.
After seeing Atletico Madrid's name in group B, it was certainly one of the groups Liverpool fans would have preferred to avoid.
The last time the two sides met, Atletico came out on top in heart breaking fashion.
Atletico's 1-0 victory at home gave them something to hold on to at Anfield for the second leg.
However two goals from Marcos Llorente and one from Alvaro Morata meant the tie finished 4-2 on aggregate, knocking out Klopp's side who were the current reigning champions.
However, on a more positive note, the group stage draw means Liverpool will return to the Wanda Metropolitano, the stadium where a sixth Champions League title was secured for The Reds.
The match up also presents an opportunity for Klopp's side to get revenge.
On paper, this is the hardest team Liverpool will face. Diego Simeone has become known over the past few years for sculpting one of the most difficult teams to beat.
Whilst defending, the team sets up with very little space in between the defence and midfield, making it very difficult to create opportunities for strikers. This is where Liverpool struggled, particularly in the first leg.
Since the two sides met, Atletico signed former Liverpool striker, Luis Suarez. The Uruguayan's impact was undeniable, helping Atletico win their first La Liga title since 2014.
Porto have become a familiar name to Jurgen Klopp's team over the past couple of seasons, having faced them consecutively in the 2018 and 2019 Champions League knockout stages - coming out victorious both times.
In 2018, Liverpool beat the Portuguese club 5-0 on aggregate, with all five goals coming away from home at the Estadio do Dragao, where Sadio Mane also grabbed his first hat-trick in a Liverpool shirt.
The following season, on route to the final in Madrid, The Reds once again beat Porto by a five goal deficit - 6-1 on aggregate - after a thrilling 4-1 victory in Portugal.
Despite the recent success against the two time Champions League winners, Porto still pose a significant threat, as shown by their performances against Juventus in last year's competition.
A late away goal deep into the second half of extra time was enough to knock out The Old Lady 4-4 on aggregate.
In this tie, it was Porto's defensive display which was so impressive, keeping Cristiano Ronaldo quiet over two legs.
Juventus struggled to break down Porto's defence which was so deep and so rigid, something which Klopp is used to facing in the Premier League.
One player Liverpool will have to watch out for is Otavio, who was linked with a move to Merseyside earlier in the window.
The Brazilian midfielder was involved in 17 goals in all competitions, making him a solid threat to Liverpool's defence.
Completing Liverpool's group is the Italian giants, AC Milan, a side who will need no introduction.
Milan were of course the victims of the miracle of Istanbul, where Liverpool won their fifth Champions League title after trailing 3-0 at half time.
In Athens two years later, Milan did get their revenge, beating Liverpool 2-1 to win their seventh Champions League trophy, and remain the second most successful club in the competitions history.
However, Milan aren't quite the club they used to be, and are playing in the Champions league for the first time since the 2013/14 season. Since then they have struggled in the Serie A, only managing to qualify for the UEFA Europa League three times.
They have improved considerably recently, finishing second in the league.
One of Milan's star performers over the past two seasons is Theo Hernandez.
The French left-back has been a constant threat to the oppositions defence with his pinpoint crossing. Hernandez has also been amongst the goals scoring seven in 33 league appearances.
Franck Kessie has also been a vital part of their recent resurgence, scoring 13 goals and assisting six in 37 Serie A appearances last season.
The Ivorian also had a goal questionably disallowed at Old Trafford, in a round of 16 Europa League tie against Manchester United last season, and will no doubt cause problems for all the teams in group B.