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.