This volume contains the exploratory papers presented at the 27 th International Workshop on Cellular Automata (CA) and Discrete Complex Systems (DCS), AUTOMATA 2021, held on July 12-14, 2021, at the Centre International de Rencontres Mathématiques (CIRM) in Marseille, France. The conference is the official annual event of the International Federation for Information Processing (IFIP), Technical Committee 1, on Foundations of Computer Science, Working Group 5, on Cellular Automata and Discrete Complex Systems.

AUTOMATA is an annual series established in 1995 as a collaboration forum between researchers in CA and DCS, and as the official annual event of the International Federation for Information Processing (IFIP), Technical Committee 1, on Foundations of Computer Science, Working Group 5, on Cellular Automata and Discrete Complex Systems.
Current topics of the conference include, but are not limited to, dynamical, topological, ergodic and algebraic aspects of CA and DCS, algorithmic and complexity issues, emergent properties, formal languages, symbolic dynamics, tilings, models of parallelism and distributed systems, timing schemes, synchronous versus asynchronous models, phenomenological descriptions, scientific modeling, and practical applications.

This year's event takes place on July 12-14, 2021, in a hybrid mode, both online and at the Centre International de Rencontres Mathématiques (CIRM) in Marseille, France.
It is colocated with the Workshop on Automata Networks, and both events are the opportunity to jointly celebrate Eric Goles's 70th birthday, from Universidad Adolfo Ibañez, Chile, who is a prominent actor in both communities.

More information about the conference can be found at https://automata2021.lis-lab.fr/.

We thank the authors and committees for their contributions.