This FLOPS 2026 constitutes the proceedings of the 18th International Symposium on Functional and Logic Programming, FLOPS 2026, held in Tsukuba, Japan, in May 26-28, 2026.

The 14 full papers and 2 invited talks presented in this volume were carefully reviewed and selected from 25 submissions. They were organized in topical sections as follows:.Lambda Calculus and Type Theory; Term Rewriting; Programming Language Semantics; Programming Language Compilers; Functional; Logic and Functional-Logic Programming; SAT solving; and applications thereof.