Factor X is the Spanish version of the British television music competition The X Factor, created by Simon Cowell. The show, first aired on Cuatro between 2007 and 2008, following the British format from 2005 to 2006, with three categories, mentored by one judge each, whom choose the acts to represent the category in the live shows. The judges were singer and DJ Miqui Puig, music manager and headhunter Eva Perales and music radio producer Jorge Flo. Nuria Roca hosted the show. The first season was won by María Villalón. The second season was won by Vocal Tempo.

On 27 September 2017, Telecinco announced the revival of the series with the production of a new season. It was hosted by Jesús Vázquez.^[1] On 19 December 2017, it was announced that the panel of mentors would consist of singer Laura Pausini, publicist and television personality Risto Mejide, radio host Xavi Martínez, and musician and music producer Fernando Montesinos.^[2] Nando Escribano hosted the side show Xtra Factor, which aired on Divinity.^[3] In 2019 it was initially announced that Telecinco renewed the series for a fourth season,^[4] but Fremantle España CEO Nathalie García stated later in the year that there were no plans for a new season.^[5] In January 2024, it was reported that Telecinco was once again planning to relaunch the format, with a fourth season due to begin in the spring.^[6]

  "16-24s" category
  "Boys" category
  "Girls" category
  "Over 25s" category
  "Groups" category
  Categories not used in this season

In each season, each judge is allocated a category to mentor and chooses acts to progress to the live shows. This table shows, for each season, which category each judge was allocated and which acts he or she put through to the live shows.

Key:

  – Winning judge/category. Winners are in bold, eliminated contestants in small font.

(*) Categories were not used in this season.

The first season started its run on Sunday 13 May 2007. The show was then broadcast nightly with 'Los Castings' (the auditions), which lasted until 20 May 2007. From the 21 May until 27 May 2007 'La Selección Final' (final selection) was shown, again nightly. On 28 May 'Las Galas' (live shows) began. Factor X proved successful for TV channel Cuatro. It achieved an average rating of 12.3%. Factor X live shows were shown at 10pm every Monday evening.

The second season started its run 1 September 2008 with the auditions. The first "gala" or live show was aired on 22 September, on primetime. In a similar fashion to the last seasons in the original British version, each gala had a different theme (number-one hits or 80's music, for example). Five acts were chosen for the finals in each category, and an additional contestant was chosen in the middle of the season through Internet auditions

The third season premiered on Telecinco on 13 April 2018, ten years after its run on Cuatro.^[7]

Telecinco initially announced a fourth season for 2019.^[4] Alejandro Sanz and Isabel Pantoja were offered a slot in the jury,^[21] but both reportedly declined.^[22] In November 2019, the CEO of Fremantle Spain, Nathalie García, stated that there were no plans for a new season.^[5]

After the format stayed dormant for five more years, in January 2024 it was reported that Telecinco was working on bringing back the format for a fourth season, which was tentatively slated to begin in the spring of the same year.^[6] In February, Ion Aramendi was announced as the new host.^[23] By early March, the new panel of judges was confirmed to be made up of Willy Bárcenas, Lali, Abraham Mateo and Vanesa Martín.^[24] This season abandoned the format's traditional division in categories, meaning the four judges will form their teams including either solo acts or groups, with no gender- or age-based restrictions.^[25]

A few weeks after the first season ended, eventual winner María Villalon released a debut EP entitled María Villalon, an album with all the songs she sang whilst in the competition. A few months later, she released her debut album Te Espero Aquí, which made the Spanish top 40 album chart, just like her debut LP did. But she wasn't the only one who received a record deal, runner-up Angy released her debut self-titled album a couple of weeks after Villalon's debut album release. She also began an acting career starring in the teen drama television series Física y Química, aired on Antena 3. 3rd placed Walter released a single, but it didn't see much success. Angy's debut single 'Sola En El Silencio' was a major hit across Spain, making the top 20 in Spanish Los 40 Principales. In turn, Maria Villalon's first two singles 'Aguita De Abril' and 'Te Espero Aqui' failed to gain chart stardom, but her second album saw the success of its lead single 'La lluvia' which made it into the top 5 in Los 40 Principales.

Months after the contest finished, 6th placed Leire Martínez's popularity boosted as she was chosen to replace Amaia Montero as the new lead singer of La Oreja de Van Gogh, one of the best-selling pop bands in Spain and Latin America.^[31] Her first album with the band, A las cinco en el Astoria, was released on 2 September 2008 reaching the number-one spot in the Spanish charts.

8th placed Ailyn submitted a song to Salvemos Eurovisión, the Spanish selection for the 2008 Eurovision Song Contest, but failed to get to the final round. Later that year, she was chosen to be the new female vocalist of the Norwegian Gothic Metal band Sirenia, working with them until 2016.^[32]

After the third season ended, judge Laura Pausini invited some of the contestants, including her pupils Samuel Hernández and series winner Pol Granch, to serve as opening acts for her upcoming world tour.