Thomas Castaignde was born in Mont-de-Marsan, Aquitaine on the 21st January 1975. He is a former French rugby union footballer who was renowned as one of the most talented backs of his era.

He played as a junior and senior for Stade Montois in various positions, initially as fly-half or centre, and latterly as fullback. He joined Toulouse to help them win French titles in three successive seasons, and lifted the inaugural European Cup with the club.

Thomas Castaignde entered the international scene in 1995 when his drop goal defeated England in the final minute of a Five Nations. Having joined Castres Olympique in preparation, in 1999 he was forced to pull out of the 1999 Rugby World Cup with a thigh problem.

Castaignde joined Saracens in 2000 but in November of that year he suffered an Achilles injury while warming up for France against Australia. The injury kept him out for 18 months, until April 2002. In 2003, he was dropped from the national team, with Bernard Laporte preferring Brian Liebenberg, and not returning until November 2005 against Australia when he appeared as a substitute in a 26-16 win.

Developing his career in preparation for his retirement, Castaignde became a rugby union columnist for The Guardian, a television pundit for the French TV channel Canal and occasionally ITV Sport, and started an association and occasional work with French banking group Socit Gnrale. On 10 May 2007, despite offers to return to France with various clubs, Castaignde announced his retirement from the sport after the 2007 Rugby World Cup in September, and pursue a career in banking in London.

Thomas now has a full time sales job at UBS Ltd in London.