ReLaX is an international joint research unit of CNRS, Université de Bordeaux, École Normale Supérieure Paris-Saclay, Chennai Mathematical Institute and the Institute of Mathematical Sciences.

As a CNRS unit, ReLaX is CNRS IRL 2000. It is attached to the INS2I (Institute for Information Sciences). As of 2023, it is also supported by INSMI (Institute for Mathematical Sciences)

ReLaX was created on January 1, 2017. Its director is Madhavan Mukund. Its deputy director is Pascal Weil.

ReLaX is a sequel and an amplification of the earlier LIA INFORMEL (Indo-French Formal Methods Lab, 2012-2016), a joint international lab between the same partners, dedicated to research in formal methods.