Celta Vigo have played many seasons in La Liga, but have never won a league title or the Copa del Rey. One of their best seasons was 1970–71, when they finished unbeaten at home and were known as the "giant-killers." Celta came sixth that season and qualified for the UEFA Cup for the first time. More recently, the club finished in their best-ever position of fourth in 2002–03, qualifying for the 2003–04 UEFA Champions League, where they were eliminated by Arsenal.
R.C. Celta de Vigo was formed as a result of the ambition of Vigo's teams to achieve more at national level, where the Basque sides had been their bête noire in the Spanish Championship. The idea was to merge both teams to create a more powerful team at national level. The standard-bearer of this movement was Manuel de Castro "Handicap", a sports writer for the Faro de Vigo who, from 1915, started to write in his articles about the need for a unitarian movement. The slogan of his movement was "Todo por y para Vigo" (All for and to Vigo), which eventually found support among the managers of Real Vigo Sporting and Real Club Fortuna de Vigo. It was backed unanimously when De Castro himself presented the motion at the assembly of the Royal Spanish Football Federation in Madrid, on 22 June 1923.
On 12 July 1923, at the AGMs of Vigo and Fortuna held at the Odeon Theatre and in the Hotel Moderno, respectively, the merger was approved. Thus the "Team of Galicia" was born, as it was dubbed. In the last AGM of Fortuna and Vigo to approve the formation of a new club held on 10 August 1923, the members decided upon the team's name. Various names were suggested:
Real Unión de Vigo
Real Club Olimpico
The last name was popular but they eventually decided on Real Club Celta, an ethnic race linked to Galicia (see Celts). The first president of Celta was Manuel Bárcena de Andrés, the Count of Torre Cedeira. At this AGM, the squad was also decided, which numbered 64 players in total, that included some notable players from both Fortuna and Vigo:
Goalkeepers: Isidro, Lilo and Rubido
Defenders: Otero, Pasarín, Juanito Clemente, Daniel y Kaíto
The late 1990s (1997—2003) saw the best results in Celta's history, in which they managed to consolidate themselves as a top-six league side, culminating in 2001–02, when they did not fall below sixth the whole season. They were dubbed EuroCelta by the Spanish press. In February 2001 the IFFHS declared Celta the best team of the world during that period, as a consequence of the fantastic results. The most important players during that period were Alexander Mostovoi, Valery Karpin and Haim Revivo. The squad counted also with other international players such as the goalkeeper Pablo Cavallero, the midfielders Claude Makélélé and Mazinho, the winger Gustavo López or the strikers Catanha, Luboslav Penev and Benny McCarthy, among others.
Celta had a dramatic reversal of fortune in 2003—04. The previous season, they finished fourth in the league, putting them in the third qualifying round of the Champions League. Celta entered the group phase after eliminating Slavia Praha, and eventually reached the last 16 before being knocked out by Arsenal. However, their domestic form was disastrous, and they finished second to the last in La Liga, so they were relegated to the second level. Although their squad was heavily dismantled, they earned a return to the top flight at the first attempt, after finishing second in 2004-05's Segunda.
In the 2005–06 season, they finished sixth earning a return once more to the UEFA Cup. They made it to the last 16 in that competition as well, before losing to Werder Bremen.
In the 2006—07 season, Celta finished in 18th position and were relegated to Segunda División. At the end of June 2007, Celta avoided going into administration. However, if an agreement was not put in place between the club and its creditors within three months, then courts would declare the liquidation of the club's assets.
Due to the huge debt, the club was forced to sell many players and make tremendous cuts in the club's finances. Since then, they have been relying mainly in the reserves team, combined with some inexpensive signings. During the first three seasons in Segunda División the club struggled hard to avoid relegation, amid fears of the club's disappearance. This was a period of high instability, with constant changes of managers and players. In the season 2010–2011, the signings of the striker David Rodríguez, the winger Enrique de Lucas and the manager Paco Herrera turned the situation and the club finished sixth, performing a fantastic season and qualifying for the promotion. Nevertheless, they were eliminated in the first knockout by Granada CF on the penalty shootout, after an aggregate of 1–1 .
Celta Vigo's original team strip consisted of a red shirt, black shorts and blue socks. This was later changed at an unknown date to the traditional sky blue and white strip – representative of the Galician flag.
Celta Vigo have the longest-running sponsorship deal in Spanish football; Going back to the 1985–86 season, Citroën, the biggest employer in Vigo, and in Galicia, has been their official shirt sponsor. Their business deal with kit supplier, Umbro, was also one of the longest-running ones – Umbro's regional headquarters are based in nearby Redondela.
Like many other Galician clubs, such as Compostela and Racing Ferrol, the club badge is based on the red cross of Saint James. On top of the cross sits a sky blue shield with two letter Cs (Club Celta). In 1923, Celta became one of several Spanish football clubs that were granted patronage by the Spanish crown and thus entitled to use Real (Royal) in their names and the royal crown on their badge. This right was granted to Celta by Alfonso XIII and the club subsequently became known as Real Club Celta de Vigo. During the Spanish Second Republic (1931—1936) the title Real was removed from the club's name and the royal crown was taken off the club crest, however it was to return under the Spanish State.