This book constitutes the refereed proceedings of the 16th International Conference on Social Computing and Social Media, SCSM 2024, held as part of the 26th HCI International Conference, HCII 2024, which took place in Washington, DC, USA, during June 29-July 4, 2024. The total of 1271 papers and 309 posters included in the HCII 2024 proceedings was carefully reviewed and selected from 5108 submissions. The SCSM 2024 proceedings were organized in the following topical sections: Part I: Designing, developing and evaluating social media; user experience and user behavior in social media; AI and language models in social media; Part II: Social media in learning, education and culture; social media in business and ecommerce; Part III: Computer-mediated communication; social media for community, society and democracy.