BEL6GICA is a concerted action that combines the contributions of the best academic research groups and institutes in this field across Belgium to map the landscape, identify specific needs, review complementarities and gaps, and establish a roadmap to maximize the impact and opportunities for Belgium in a future world where a region's competitiveness will depend heavily on the frictionless use of articifial intelligence (both centrally and at the edge of the network among citizens, government and business), the associated public and private data flows, the link between the physical and virtual worlds, and the know-how around it. Moreover, we will take in account both sustainability for 6G and 6G for sustainability. As Nokia's CEO said: "There is no green without digital." This is the world of 6G.