According to the invention, there is provided a novel soybean variety designated XR31C09. This invention thus relates to the seeds of soybean variety XR31C09, to the plants of soybean XR31C09 to plant parts of soybean variety XR31C09 and to methods for producing a soybean plant produced by crossing plants of the soybean variety XR31C09 with another soybean plant, using XR31C09 as either the male or the female parent.