This book constitutes the proceedings of the 23nd Asian Symposium on Programming Languages and Systems, APLAS 2025, held in Bengaluru, India, October 27–30, 2025.

The 13 full papers presented here were carefully reviewed and selected from 28 submissions.They were focused on the following topical sections: Type Systems, Safety, and Verification; Control, Effects, and Decidability; Quantum Programming and Logic; Program Analysis, Specifications, and Decision Procedures; AI and Compiler Optimisation for Performance.