Sylvain Marconnet is a French rugby union footballer who played for Biarritz Olympique having signed from Stade Français in the Top 14 club competition in France. His usual position is prop. Marconnet has played for France, including representing them at the 2003 Rugby World Cup in Australia.

Biarritz Olympique Pays Basque, usually known simply as Biarritz, is a French professional rugby union team based in the Basque city of Biarritz, Nouvelle-Aquitaine which competes in the Pro D2, the second division of French rugby. Biarritz plays its home matches at the Parc des Sports Aguiléra, which is a multi-use stadium in Biarritz and which has a capacity of around 13,500 people, though for games that need a larger capacity, Biarritz may play at the Estadio Anoeta in San Sebastián. Biarritz play in red and white colours. Biarritz won a number of major honors, including the French championship on five occasions.