The Four Nations tournament (Cuatro Naciones in Spanish, Quatre Nacions in Catalan and Lau Nazioen in Euskara) is the annual team chess tournament organised alternately by Euskal Xake Federakuntza in Donostia-San Sebastián and Federació Catalana D'Escacs in Caldes de Malavella. Catalonia (Catalunya) and The Basque Country (Euskadi) are permanent participants while every year two other national teams are invited to participate, Argentina being most successful guests to have won the tournament twice until today. The autonomous communities of the Basque Country and Catalonia are eligible to field their teams and they play under their own flag, something that is not permitted in the official international tournaments (they are not members of FIDE either). Notably Spain has never been invited to play, even though there were some prominent members of national Spanish teams participating.

The level of play is fairly high, with the best players rated within 2500-2600 zone. The events are round robin on four boards, so there are 3 rounds every year, and usually the run is quite close. Notably no player ever managed to score a perfert 3/3, but two Basque players, Juan Gómez Esteban and Sant González took part in all tournaments from the very beginning.

Winners 2003-2008 (men): 3x Catalonia, 2x Argentina, 1x Romania