This volume contains the papers presented at the 9th International Joint Conference on Automated Reasoning, IJCAR-2018, held  on July 14-17, 2018 in Oxford, United Kingdom, as part of the Federated Logic Conference, FLoC-2018.

There were 125 abstracts submitted to IJCAR, resulting in 108 complete submissions. Each submission was assigned to 3 program committee members and received at least 3 reviews. The committee accepted 46 papers in total, 38 full papers and 8 system descriptions. In addition, the program includes two invited talks by Erika Abraham and Martin Giese, and accomodates a number of FLoC central events.

IJCAR is the premier international joint conference on all aspects of automated reasoning, including foundations, implementations, and applications, comprising several leading conferences and workshops. It was first held in Sienna, Italy, in 2001, uniting CADE, the Conference on Automated Deduction, TABLEAUX, the International Conference on Automated Reasoning with Analytic Tableaux and Related Methods, and FTP, the Workshop on First-Order Theorem Proving. Since 2004, IJCAR has been held every second year, alternating with separate meetings of its constituent conferences. In 2018, IJCAR unites CADE, TABLEAUX, and FroCoS, the International Symposium on Frontiers of Combining Systems, and, for the fourth time, is be part of the Federated Logic Conference. IJCAR also hosts the CADE ATP System Competition and 11 workshops.

IJCAR acknowledges the generous sponsorship of EurAI, the European Association for Artificial Intelligence (https://www.eurai.org/), for supporting in part our invited speakers.

We would like to thank the organizers of IJCAR, FLoC, and associated events, but in particular the members of the IJCAR program committee and the additional external reviewers. They have provided high-quality reviews, and nearly always done so on time with no more than the usual reminders.

The PC chairs also would like to acknowledge EasyChair. The system was extremely supportive for nearly all major task, including the reviewing and selection of papers, the organisation of the program, and creating this proceedings volume.