After winning the Premier League for the third straight season, City's 2-1 FA Cup Final victory over Manchester United and 1-0 Champions League triumph over Inter means they have now joined the illustrious group of clubs.
Losing Champions League finalists Inter are already on the list of seven sides to have won a treble, doing so under Jose Mourinho in 2009/10.
Celtic (1966/67), Ajax (1971/72), PSV Eindhoven (1987/88), United (1998/99), Barcelona (2008/09 & 2014/15) and Bayern Munich (2012/13 & 2019/20) are the others to have won their domestic league and cup, as well as the European Cup or Champions League, in the same season.
Let's take a look at each of these legendary eight sides in turn:
Famously all born within a 30-mile radius of Parkhead, Celtic's squad of 1966/67 became the first to do the treble. In fact, they also won the Scottish League Cup, making them the only side to have won a quadruple.
It was Inter who they beat 2-1 in the European Cup final in Lisbon, recovering from going behind to a seventh-minute penalty by unlocking the famously stubborn Catenaccio defence favoured by Nerazzurri boss Helenio Herrera.
Second-half goals from Tommy Gemmell and Stevie Chalmers saw Jock Stein's side become the first British team to be crowned European champions, with the Bhoys' success at the Estadio Nacional earning them the moniker of the 'Lisbon Lions'.
Few sides have transformed football as much as the Ajax team of the early 1970s, winning the European Cup in three successive seasons between 1971 and 1973.
The middle of those marked their first season after the "Father of Dutch football", Rinus Michels, had departed for Barcelona to be replaced as coach by Stefan Kovacs.
The Romanian won the Eredivisie and KNVB Cup before guiding Ajax to a 2-0 win over Inter at Rotterdam's De Kuip, home of their bitter rivals Feyenoord.
Kovacs arguably did the impossible by making the team better than under Michels and, with Johan Cruyff and Johan Neeskens at his disposal, his decision to continue with his predecessor's philosophy of "total football" clearly paid off.
The other Dutch club to complete the treble, making the Netherlands the only nation to have had two clubs achieve the feat, PSV Eindhoven dominated the domestic scene in the late 80s, winning league and cup doubles in 1987/88 and 1988/89.
That was part of a run of six league titles in seven years but it was the 1987/88 season that stood out as they also won the European Cup.
A talented team, headlined by Ronald Koeman and coached by Guus Hiddink, beat Benfica on penalties in Stuttgart to match both Ajax and Feyenoord by being crowned continental champions.
As the only English fans to have seen their side complete the treble, the red half of Manchester will be holding its breath on Saturday when City walk out in Istanbul.
While the Citizens' push for silverware was relentless, United's was a rollercoaster, winning the league by just a point from Arsenal on the final day, while also edging out the same opponents in the semi-finals of the FA Cup before outclassing Newcastle United 2-0 in the final.
However, nothing compares to their Champions League Final victory over Bayern Munich.
Trailing 1-0 heading into stoppage-time, the Red Devils rallied, equalising through Teddy Sheringham, before Ole Gunnar Solskjaer directed a Sheringham header into the roof of the net to see United win 2-1 and lift the European Cup for the first time since 1968.
|Celtic||1966/67 - Also won the Scottish League Cup|
|Barcelona||2008/09 & 2014/15|
|Bayern Munich||2012/13 & 2019/20|
After just a single year in charge of Barcelona's B team, few knew what to expect when now-City boss Guardiola took over the Catalan club's senior team in the summer of 2008.
A treble in his first season set the standard, beating United in the Champions League Final 2-0 and then the same opponents 3-1 two years later, albeit having missed out on the treble in that campaign due to their defeat to Real Madrid in the 2011 Copa del Rey Final.
Like Guardiola, his former team-mate Luis Enrique also did the treble in his first season in charge at Camp Nou, winning La Liga by two points, before beating Athletic Bilbao in the Copa del Rey and repeating that outcome against Juventus in Berlin in June 2015.
Gerard Pique, Sergio Busquets, Xavi, Andres Iniesta, Pedro and Lionel Messi were among the homegrown players who spanned both trebles.
They were complemented by the likes of Thierry Henry, Dani Alves, Luis Suarez and Neymar during an unprecedented spell of success for the Blaugrana.
Jose Mourinho's finest season as a coach came in 2009/10 when he guided Inter to a treble of Serie A, Coppa Italia and Champions League.
A 1-0 final day win at Siena saw the Nerazzurri take the Scudetto title ahead of Roma, having previously beaten the Giallorossi by the same scoreline in the final of the Coppa Italia.
However, Mourinho's magic was on full display in the Champions League as he engineered two-legged wins over former club Chelsea, a talented CSKA Moscow side and most famously, Barcelona, who had overlooked him to appoint Guardiola two years earlier.
His team's 3-1 first-leg semi-final win at San Siro paved the way for a backs-to-the-wall 1-0 defeat at Camp Nou, in which they lost Thiago Motta to a second yellow card after just 28 minutes.
By the time they reached the Bernabeu for the final against Bayern, it felt inevitable they would win the treble and Diego Milito's brace fired them to a 2-0 success.
Mourinho would not have to wait long to return to the Bernabeu, deciding that the win over Bayern signalled the perfect time to step down as Inter boss before taking over at Real later that summer.
Having been one game from winning the treble under Louis van Gaal in 2010, Bayern Munich suddenly became a nearly club.
They twice finished as runners-up domestically to Borussia Dortmund, before being hit by heartbreak as they lost the 2012 Champions League Final on home turf at the Allianz Arena to Chelsea.
The board kept faith with Jupp Heynckes after the Blues defeat and were repaid as his team won the 2012/23 Bundesliga by 25 points, before beating Dortmund 2-1 in the finals of both the DFB-Pokal and Champions League.
They could not repeat Heynckes' success under Guardiola and, while other high-profile names followed, they finally clicked under Hansi Flick, who replaced Niko Kovac in November 2019.
Flick was previously a midfielder for the club, making his team's success in 2019/20 even more popular, rounding off their treble with a 1-0 Champions League Final win over Paris Saint-Germain in Lisbon.
Pep Guardiola's Man City are the latest side to etch themselves into the history books as Treble winners, after winning the Champions League, Premier League and FA Cup in a truly astounding season.
After trailing Mikel Arteta's Arsenal for several months in the Premier League title race, the quality and winning pedigree of City ultimately told in the end as they scooped their third consecutive title by a margin of five points.
FA Cup success would prove extremely sweet for the Citizens after downing fierce rivals Man United 2-1 in the final at Wembley, with German skipper Ilkay Gundogan netting a brace on the day.
Ultimately it was the Champions League trophy which City craved most having never got their hands on the competition before, and after a somewhat disjointed performance in Istanbul all of their dreams came true with a 1-0 triumph courtesy of a well-taken Rodri winner.