Graph processing is becoming increasingly prevalent across many application domains. In spite of this prevalence, there is little research about how graphs are actually used in practice. We conducted an online survey aimed at understanding: (i) the types of graphs users have; (ii) the graph computations users run; (iii) the types of graph software users use; and (iv) the major challenges users face when processing their graphs. We describe the responses of the participants to our questions, highlighting common patterns and challenges. The participants’ responses revealed surprising facts about graph processing in practice, which we hope can guide future research. The Ubiquity of Large Graphs and Surprising Challenges of Graph Processing: A User Survey