He is the cousin of the deceased former footballer Ludovic Quistin and of Mathieu Bastareaud, a French rugby union centre playing for Lyon.

[5][6] A graduate of the French football academy at Clairefontaine, Gallas started his professional career at second division Caen, helping them to promotion as champions in 1996.

The Blues also made the semi-finals of the UEFA Champions League that year, but were knocked out by Liverpool 1–0 in controversial circumstances—Gallas cleared the ball, after it was adjudged to have crossed the line.

[13][14] Gallas scored some vital goals against Liverpool, Tottenham Hotspur and Manchester United as Chelsea retained their title in the 2005–06 Premier League season.

He refused to sign a new contract with Chelsea on improved terms after saying the club did not offer him enough money and expressed a wish to play in the Italian Serie A, with Juventus and Milan both interested.

PFA Chief Executive Gordon Taylor declared that the whole episode has left a "bad taste in the mouth" and that Chelsea's statement should be taken "with a large pinch of salt.

"[citation needed] Gallas signed a four-year contract with Arsenal, where he took the number 10 shirt vacated by the recently retired Dennis Bergkamp.

In the end I thought it might be a good idea to give the number ten to a defender, because a striker would suffer a lot with the comparison with Dennis.

[25] Gallas suffered a groin injury in the game against Blackburn Rovers on 19 August, but returned to play for Arsenal in their 2–0 victory over Bolton Wanderers on 20 October.

[28] Gallas drew some criticism as a result of his actions in a 2–2 draw against Birmingham City at St. Andrew's on 23 February 2008, a game that saw Eduardo's leg broken following a challenge by Martin Taylor (who was subsequently sent off).

After the final whistle, Gallas sat down on the pitch as the rest of the players left the field before being consoled by manager Arsène Wenger.

Amid speculation that Gallas would be replaced as club captain following his behaviour during the Birmingham game, Wenger said that he would consider the matter at the end of the season.

On 10 April 2009, it was confirmed that Gallas would miss the remainder of the season after damaging the medial ligament in his right knee during the 2008–09 UEFA Champions League quarter-final first leg tie against Villarreal.

He formed a partnership with Belgian centre back Thomas Vermaelen,[39] Arsenal's only major summer signing, and the pair scored seven goals between them in their first eight league games.

He suffered an injury-hit second half of the season and did not play for over two months; he was surprisingly included in the starting line up against Barcelona only to get stretchered off before half-time with a recurrence of the injury.

[43] On 20 August 2010, Tottenham Hotspur manager Harry Redknapp confirmed that Gallas was set to join the club and described the move as a "no-brainer.

In the Champions League knockout stages, he put in two commanding performances against Milan to set up a quarter-final tie against Real Madrid in the club's first attempt in the competition.

[50] During the 2011–12 Premier League, Gallas suffered several injuries that hindered his playing time for the season, making just 19 appearances for Tottenham during the campaign, particularly in light of the competition for the center-back spot with Michael Dawson and Ledley King.

Gallas joined the league following the arrival of other international players, Alessandro Del Piero, Emile Heskey and Shinji Ono.

He also played for the France U-20 team in the 1997 FIFA World Youth Championship along with Thierry Henry, David Trezeguet, Nicolas Anelka, Mikaël Silvestre and Willy Sagnol.

[59] He was included in France's squad for the 2003 FIFA Confederations Cup and played the full 90 minutes as Les Bleus defeated Cameroon 1–0 in the final.

Gallas was ever present as France finished runner-up in the 2006 FIFA World Cup, losing on penalties to Italy at the Berlin Olympiastadion.

[63] On 6 June 2011, aged 33 and with 84 caps to his name and 5 goals he announced his retirement from international football with immediate effect after he had not been selected in the year since the World Cup.