This book encompasses a diverse array of contemporary topics in chaos theory nonlinear dynamics and applications of theirs, including theory of nonlinear dynamics, mathematical chaos, physics and astronomy, circuits and systems, memristors, complex networks, pattern formation, biological systems, time-series analysis, and the intricate behaviors of neural, psychological, psychosocial, socio-economic, and global systems. The conference serves as a platform for scientists, engineers, economists, and social scientists to come together and discuss the latest advancements and findings in the realm of nonlinear and complex (chaotic) system behavior. The 6th International Interdisciplinary Chaos Symposium on Chaos and Complex Systems, held from May 8 to May 10, 2025, in Istanbul, Turkey, continued a tradition of dialogue and discovery bringing together researchers, engineers, economists, and social scientists from around the globe in a shared effort to explore the latest developments and applications in nonlinear science and complexity. As expected, it expanded its scope to cover a broader range of subjects such as unconventional cryptography, physical unclonable functions, reservoir computing, and quantum information, further enriching the interdisciplinary exchange of ideas and research.