ICOOOLPS 2025 – Implementation, Compilation, Optimization of Object-Oriented Languages, Programs and Systems: Preface.

Optimization of Object-Oriented Languages, Programs and Systems (ICOOOLPS 2025), held in Bergen, Norway, on July 2, 2025, co-located with ECOOP 2025.ICOOOLPS brings together researchers and practitioners working in the field of programming language implementation, compilation, and optimization.Although its origins are rooted in object-oriented programming, the workshop now embraces a broader perspective, encompassing a wide range of language paradigms and runtime technologies.This year, we received eight submissions: seven full research papers and one lightning talk.Four full papers were accepted for presentation at the workshop, covering topics such as language runtime systems, compilation techniques, and performance engineering.The accepted contributions are:-Cellato: a DSL for Cellular Automata based on C++ Template Meta-programming -Matyáš Brabec, Jiří Klepl, Martin