Since La Liga was founded in 1929, the Spanish top flight has witnessed many legendary teams, from the classic Real Madrid side of the 1950s through to Pep Guardiola's masterful Barcelona and beyond.
One measure of greatness is the ability to perform consistently without faltering or losing concentration, so among all the club titles and individual feats, lengthy unbeaten streaks tend to stand the test of time.
While the mark for most consecutive home games without a loss stands at a staggering 121 - put together by Real Madrid from February 1957 to March 1965 - the overall record is considerably lower.
Carlo Ancelotti's current Madrid team looked on course to make history as they recorded a 42-match unbeaten run which stretched over more than a year, before taking on Clasico rivals Barcelona in a game that could have seen then equal the all-time longest unbeaten streak - a record held, inevitably, by Barca themselves.
However, Hansi Flick's Barcelona side inflicted a historic and humiliating home defeat on record-chasing Real by running out 4-0 winners at the Bernabeu on Saturday evening, dealing Madrid their first league defeat since September 2023.
With Madrid's hopes of overhauling their great rivals falling agonisingly short, here Sports Mole counts down the longest unbeaten streaks in La Liga history.
5. Real Madrid (30 games, 1987-1988)
© Imago
Until this year, Real Madrid's longest unbeaten run in La Liga was a relatively modest 30 matches, starting at the end of the 1987-88 season and continuing into 1988-89.
In the era of legendary Mexican striker Hugo Sanchez and German midfielder Bernd Schuster - the latter of whom later returned as manager - Los Blancos were untouchable in Spanish football for several months.
Backed up by 'La Quinta del Buitre' - Manolo Sanchis, Rafael Martin Vazquez, Michel and Miguel Pardeza, five talented graduates of Madrid's youth academy - and helmed by Dutch coach Leo Beenhakker, they were quite a force to be reckoned with.
At the end of their 1988-89 campaign, Real finished as champions for the fourth consecutive season, five points ahead of runners-up Barcelona.
Furthermore, they completed a superb domestic treble by winning both the Copa del Rey and the Supercopa.
4. Barcelona (31 games, 2010-2011)
© Imago
In the season after several Spain stars - such as Xavi, Carles Puyol and Andres Iniesta - finally ended La Roja's wait to lift the World Cup, a team widely considered one of the greatest club sides of all time stayed undefeated for many months in La Liga.
Pep Guardiola's team - described by legendary Manchester United manager Sir Alex Ferguson as the best he had ever faced - were peerless at the time, with Lionel Messi fast becoming an iconic figure in Catalonia.
Of course, even the greatest fail occasionally, and on 30 April 2011, Barca's unbeaten run finally came to an end with a 2-1 loss to Real Sociedad at Anoeta.
Nevertheless, a 3-1 Champions League final triumph over Ferguson's Manchester United one month later more than made up for that defeat, and Guardiola's squad are rightly remembered as having touched the pinnacle of football possibility.
3. Real Sociedad (38 games, 1979-1980)
© Imago
For 38 years Real Sociedad's record stood alone, as the last in a long line that had eventually succumbed to either Barcelona or Real Madrid.
Alberto Ormaetxea's squad featured Luis Arconada in goal, captain Inaxio Kortabarria at centre-back and Periko Alonso (father of another club legend, Xabi Alonso) running shifts in the engine room.
As they took the fight to Madrid for top spot in La Liga, the Basque club recorded several draws but stayed undefeated, most memorably coming from behind to beat Barca 4-3 in October 1979 with two goals in the last 10 minutes.
La Real were still unbeaten with just two games left to play in the 1979-80 season, but they ultimately slipped up at Sevilla, conceding an 83rd-minute goal that shattered hearts across San Sebastian.
Not only did they lose their long streak without defeat, but they also lost the title. Showing great heart, though, La Real bounced back from such a setback in style, going on to win the next two Spanish titles.
2. Real Madrid (42 games, 2023-24)
© Imago
Ancelotti's Real Madrid side reached a run of 42 La Liga games without defeat from September 2023 to October 2024, surpassing Real Sociedad's 38-game sequence and moving outright second on the list by beating Alaves 3-2 at the Bernabeu in September 2024.
Inspired by Vinicius Junior, Jude Bellingham, and later Kylian Mbappe, they effectively went unbeaten for more than a full league campaign, split between two seasons.
City rivals Atletico Madrid inflicted the last defeat on Ancelotti's men in the league prior to their run, and they went into El Clasico at home on October 26, 2024 with the prospect of equalling Barcelona's all-time record against the Catalan giants themselves.
However, the match soon became historic for the wrong reasons as Barcelona ran riot in the second half en route to a famous 4-0 victory at the Bernabeu, boosting their title hopes, emphatically claiming bragging rights and also protecting their record all in one fell swoop.
Nonetheless, across their club-record run, the European champions' numbers were immensely impressive: they posted 31 wins and 11 draws, scoring 97 goals in the process.
1. Barcelona (43 games, 2017-18)
© Imago
The all-time milestone that Ancelotti's side were chasing is held by old foes Barcelona, and was set between April 2017 and May 2018.
Barca's streak was a shared effort between Luis Enrique (seven games at the end of the 2016-17 season) and Ernesto Valverde, who started his time in charge of the Blaugrana with 36 games undefeated in La Liga.
Luis Enrique signed off with a run of seven successive victories, the first of which came against Real Sociedad at Camp Nou, with goals from Lionel Messi and Paco Alcacer setting them on the way to their historic achievement.
Valverde's team then came desperately close to completing an 'invincible' season, after recording 27 wins and nine draws. However, on 13 May 2018, with Barca already crowned Spanish champions, an incredible 5-4 away defeat to Levante brought the curtain down on their remarkable run.
Nonetheless, an all-star team featuring prime Messi, Luis Suarez and Neymar had scored no fewer than 122 goals in the process, while also keeping 19 clean sheets.
