SUMMARY The International Conference on the Molecular Biology and Pathogenesis of the Clostridia (Clostpath) has been the leading venue to bring together scientists, clinicians, and pathologists at the forefront of research on the molecular biology of clostridia and their role in health and disease. In keeping with this tradition, Clostpath12 will cover all fundamental and translational aspects of clostridial-dependent pathogenesis. Topics will include virulence gene regulation, virulence factor structure and mechanism, host-pathogen-microbiome interactions, spore dynamics and transmission, the development of new technologies to study clostridial organisms, as well as innovations designed for the detection, diagnosis, treatment and prevention of clostridial-caused diseases. The meeting will take place September 13-16, 2021 in Banff, Alberta, which is located in the heart of the Canadian Rockies. The programming for Clostpath12 is deliberate in its focus on diversity and inclusion as well as providing opportunities to young scientists. At Clostpath conferences, there are traditionally 9 sessions, with 12-20 invited speakers – all plenary (no parallel sessions). Approximately 25 additional oral presentations will be selected from submitted abstracts. The Organizing Committee, the International Steering Committee, and the list of invited speakers reflect the full geographic, scientific, and ethnic/gender/racial diversity of the Clostpath community. There will be ~150 posters presented, divided over two poster sessions. During the plenary presentations, there will also be flash talks for selected poster abstracts. To foster networking interactions, there is a social program that includes a welcome reception/working dinner on the first day of the conference, a conference dinner/party on the final evening, and optional excursions. In addition, a young scientist committee is developing trainee- specific content and activities to be integrated into the program. The objectives for the 12th Conference will be (i) to continue presenting the highest-quality, recent research on pathogenic clostridia in a forum that facilitates information exchange and future collaborations and (ii) to train and inspire young clostridial researchers who will be the next generation of leaders in the field. These objectives will be realized through two specific aims: Aim 1: Invite, support, and encourage the participation of young investigators and underrepresented scientists. Aim 2: Provide a setting that encourages collegial exchange of scientific ideas and sharing of the most current discoveries in the field.