Book excerpt: This book constitutes the refereed proceedings of the 8th International Conference on Theory and Practice of Natural Computing, TPNC 2019, held in Kingston, ON, Canada, in December 2019. The 15 full papers presented in this book, together with two invited talk, were carefully reviewed and selected from 38 submissions. The papers are organized in topical sections named: Applications of Natural Computing; Evolutionary Computation; Genetic Algorithms, Swarm Intelligence, and Heuristics; Quantum Computing and Information.