This book constitutes the refereed proceedings of the 16th International Colloquium on Theoretical Aspects of Computing, ICTAC 2019, held in Hammamet, Tunisia, in October/November 2019. The 17 revised full papers presented together with 2 keynote papers and 1 industrial paper were carefully reviewed and selected from 138 submissions. The papers are grouped in topical sections on models and transition systems; real-time and temporal logics; verification and concurrency; privacy and security; equations, types, and programming languages.