This proceedings volume contains the extended abstracts of the presentations made at the 11th edition of the conference GASCom 2018, to be held in Athens, Greece, from 18 to 20 June 2018. More speci cally, the program of the conference consists of three invited talks, 16 contributed talks and 6 poster presentations. The conference GASCom brings together researchers in combinatorics, algorithms, probabilities, and more generally mathematical computer science, around the theme of random and exhaustive generation of combinatorial structures, mostly considered from a theoretical point of view. In connection with this main theme, the conference is also interested in contributions in enumerative or analytic combinatorics, and interactions with other areas of mathematics, computer science, physics or biology. The conference is both interested in methods for random or exhaustive generation and in original results on combinatorial or algorithmic questions, whose solution has been made possible by an approach involving random or exhaustive generation. Among the main topics of the conference are the following: random and exhaustive generation of combinatorial objects, enumerative and analytic combinatorics, algorithmic aspects: analysis of algorithms, probabilistic algorithms, interactions: bio-informatics, combinatorics on words, tilings,... .