This three-volume set in LNCS constitutes the refereed proceedings of the 30th Australasian Conference on Information Security and Privacy, ACISP 2025, held in Wollongong, NSW, Australia, during July 14-16, 2025. The 54 full papers, 6 short papers and 1 invited paper included in this book were carefully reviewed and selected from 181 submissions. They were organized in topical sections as follows: symmetric-key cryptography and cryptanalysis; public-key encryption; digital signatures and zero knowledge; cryptographic protocols and blockchain; post-quantum cryptography; homomorphic encryption and applications; cryptographic foundations and number theory; privacy enhancing technologies; AI security and privacy; system security.