This book constitutes the refereed proceedings of the 9th International Conference On Secure Knowledge Management In Artificial Intelligence Era, SKM 2021, held in San Antonio, TX, USA, in 2021. Due to the COVID-19 pandemic the conference was held online. The 11 papers presented were carefully reviewed and selected from 30 submissions. They were organized according to the following topical sections: intrusion and malware detection; secure knowledge management; deep learning for security; web and social network.