Edited in collaboration with FoLLI, the Association of Logic, Language and Information, this book constitutes the refereed proceedings of the 23rd International Conference on Formal Grammar, FG 2018, collocated with the European Summer School in Logic, Language and Information in August 2018. The 7 full papers were carefully reviewed and selected from 11 submissions. The focus of papers are as follows: Formal and computational phonology, morphology, syntax, semantics, and pragmatics Model-theoretic and proof-theoretic methods in linguistics Logical aspects of linguistic structure Constraint-based and resource-sensitive approaches to grammar Learnability of formal grammar Integration of stochastic and symbolic models of grammar Foundational, methodological, and architectural issues in grammar and linguistics Mathematical foundations of statistical approaches to linguistic analysis.