This special issue entitled “Advances in Discrete Mathematics and Secure Network Technologies” brings together a comprehensive collection of research papers on current trends in discrete mathematics, algebra, combinatorics, cryptography, coding theory, and secure network technologies. This special issue contains articles that address various aspects of modern discrete mathematics and its applications in cybersecurity. Special attention has been paid to graph theory, algebraic structures, finite fields, finite groups, polynomial rings, combinatorial designs, Boolean functions, hypergraphs, semigroups, and discrete optimization. At the same time, these mathematical tools are applied to various modern cryptographic schemes, including lightweight cryptography, elliptic- and hyperelliptic-curve cryptography, lattice- and isogeny-based cryptography, homomorphic cryptography, threshold cryptography, zero-knowledge proofs, secure multiparty computation, and post-quantum cryptography.