Computer system and method for dynamically adapting a software-defined network A computer system for dynamically adapting a software-defined network is suggested. The computer system comprises a plurality of virtual domains, each virtual domain comprising a network controller to which a back-up network controller is assigned, wherein the network controller is adapted to manage a plurality of switches being assigned to the virtual domain, wherein the software-defined network is partitioned into the plurality of virtual domains, and a root controller, wherein the root controller is adapted to manage the software-defined network by dynamically adding and/or removing virtual domains based on a threshold of the software-defined network, wherein a back-up root controller is assigned to the root controller. Further, a method for dynamically adapting a software-defined network is suggested. The suggested computer system provides the advantage of a dynamical adaptation of the software-defined network and at the same time, due to the back-up controllers, an improved fault-tolerance.