Manchester United, one of the most storied football clubs in the world, has had its fair share of heartbreaking losses throughout its history. While opinions may vary among fans, here are five matches that stand out:

Champions League 2009 Final vs FC Barcelona

The 2009 UEFA Champions League Final between Manchester United and FC Barcelona is a poignant chapter in the club's history, marked by heartbreak and disappointment. Facing a formidable Barcelona side at the peak of its powers under Pep Guardiola's stewardship, Manchester United found themselves outplayed and outclassed on the grand stage of the Stadio Olimpico in Rome, Italy. Lionel Messi's virtuoso display epitomized Barcelona's dominance, as the Argentine maestro's skill and creativity left the United defense in disarray. Samuel Eto'o's clinical finish further compounded United's woes, putting Barcelona in firm control early in the match.

Despite glimpses of promise and a few fleeting opportunities, Manchester United failed to capitalize on their chances to mount a comeback. Cristiano Ronaldo's thunderous free-kick rattling the crossbar was perhaps the closest United came to clawing their way back into contention. Yet, as the final whistle blew, the scoreline stood at 2-0 in favor of Barcelona, sealing Manchester United's fate and relegating them to the role of runners-up in the 2009 Champions League.

The disappointment of losing a final, particularly on the grandest stage of European club football, reverberated through the ranks of Manchester United. The sense of missed opportunity weighed heavily on the players, staff, and supporters alike, as they had harbored hopes of retaining the coveted trophy they had triumphantly lifted the year before. Ultimately, the 2009 Champions League Final remains etched in Manchester United's collective memory as a painful reminder of falling short in the pursuit of glory, succumbing to the brilliance of Barcelona's footballing prowess on that fateful night in Rome.

Champions League 2013 Round of 16 vs Real Madrid

The first leg of the Round of 16 tie between Manchester United and Real Madrid occurred at Santiago Bernabéu Stadium. It ended in a 1-1 draw, leaving everything to play for in the second leg at Old Trafford.

The match at Old Trafford started with high intensity, with both teams eager to secure a spot in the quarter-finals. Manchester United took the lead in the 48th minute through a deflected effort from Sergio Ramos, which unfortunately went into his net. United looked solid and held onto their lead until the match's turning point.

The game took another dramatic turn in the 56th minute when Manchester United's Nani was controversially sent off by the referee, Cüneyt Çakır, for a high challenge on Alvaro Arbeloa. The decision was met with disbelief and anger from the Manchester United players and coaching staff, as Nani seemed to be contesting for the ball without malicious intent.

Champions League Manchester United

Real Madrid capitalized on the situation with a numerical advantage, and in the 66th minute, Luka Modric scored a stunning long-range goal to bring Real Madrid back into the match.

In the 69th minute, Real Madrid's star player Cristiano Ronaldo, returning to his former club, scored the winner. The goal came from a low cross by Gonzalo Higuain, which added to Manchester United's and their fans' frustration.

Despite Manchester United's efforts to find an equalizer with ten men, they could not break down Real Madrid's defense, and the match ended 2-1 in favor of the Spanish side.

The result meant that Real Madrid progressed to the quarter-finals of the Champions League. At the same time, Manchester United were left to rue the controversial red card decision that influenced the match's outcome.

Europa League Final 2021 vs. Villarreal

The match started with both teams displaying cautiousness, with Villarreal looking organized defensively and Manchester United trying to assert control in midfield. Despite some early chances for both sides, the first half ended goalless.

In the second half, Villarreal took the lead in the 29th minute through Gerard Moreno, who capitalized on a defensive error to slot the ball past Manchester United goalkeeper David de Gea. However, Manchester United responded quickly, with Edinson Cavani equalizing in the 55th minute with a fine header from a Marcus Rashford cross.

The remainder of the match saw both teams pushing for a winner, but neither could find the breakthrough. The match proceeded to extra time, with the score level at 1-1 after 90 minutes.

Extra time saw few clear-cut chances for either side, and the match ultimately went to a penalty shootout to decide the winner. The shootout was tense, with both teams converting their penalties confidently.

As the shootout progressed, it went into sudden death, with each team matching each other penalty for the penalty. However, the decisive moment came when Manchester United goalkeeper David de Gea stepped up to take their 11th penalty but saw his effort saved by Villarreal goalkeeper Geronimo Rulli.

With Rulli then converting Villarreal's 11th penalty, Villarreal emerged as the winners, clinching the UEFA Europa League title for the first time in their history. It was a heartbreaking defeat for Manchester United, who had come close to securing their first major trophy under manager Ole Gunnar Solskjaer.

Champions League 2004 Round of 16 vs FC Porto

The second leg of the UEFA Champions League quarter-final between Manchester United and FC Porto, played on April 7, 2004, at Old Trafford, is etched in football history for its drama and controversy, chiefly involving Costinha and Jose Mourinho.

Manchester United started the match with a sense of urgency, knowing they needed to overturn the deficit from the first leg, which ended in a 2-1 victory for Porto at the Estádio do Dragão, putting the Portuguese side in a favorable position heading into the return fixture in Manchester.

In the sixth minute, United grabbed the lead through a goal from Quinton Fortune, igniting hope among the home fans for a comeback. However, despite United's attacking efforts, Porto held firm defensively, frustrating their opponents for much of the match.

As the game approached its conclusion, with the aggregate score level at 2-2, tensions soared. In the 89th minute, Manchester United were awarded a controversial free-kick just outside the Porto penalty area. Cristiano Ronaldo stepped up to take the set-piece, but the referee blew his whistle before he could strike the ball.

The controversy ensued as FC Porto's goalkeeper, Vítor Baía, argued fiercely with the referee, believing the initial free-kick had been taken before the whistle. Amidst the chaos, Costinha, a Porto player, capitalized on a mistake by United's goalkeeper Tim Howard, who slotted the ball into the net.

Jose Mourinho, then the manager of FC Porto, famously sprinted down the touchline to celebrate the goal, adding to the spectacle of the moment. Despite Manchester United's protests, the goal stood, and the match ended in a 1-1 draw, with Porto progressing to the quarter-finals on the away goals rule.

Premier League 2002 vs Arsenal at Old Trafford

The match between Manchester United and Arsenal on May 8, 2002, at Old Trafford, holds significant historical importance as it marked the day Arsenal clinched the Premier League title at the home of their arch-rivals, Manchester United.

Arsenal entered the match knowing that a win or even a draw would secure them the league title, while Manchester United aimed to delay their celebrations and keep their own slim title hopes alive.

The atmosphere at Old Trafford was electric as both teams took to the field. Manchester United started the game brightly, creating several scoring opportunities, but Arsenal's defense held firm.

The decisive moment came in the 55th minute when Sylvain Wiltord capitalized on a defensive error by Manchester United's Mikael Silvestre and slotted the ball past goalkeeper Fabien Barthez to give Arsenal the lead.

Despite Manchester United's efforts to find an equalizer, Arsenal's defense, marshaled by the likes of Sol Campbell and Ashley Cole, stood firm, denying United any clear-cut chances.

As the final whistle blew, Arsenal emerged victorious with a 1-0 win, sealing their third Premier League title under the management of Arsène Wenger and their second league title at Old Trafford.