According to the invention, there is provided a novel soybean variety designated XB42K07. This invention thus relates to the seeds of soybean variety XB42K07, to the plants of soybean XB42K07 to plant parts of soybean variety XB42K07 and to methods for producing a soybean plant produced by crossing plants of the soybean variety XB42K07 with another soybean plant, using XB42K07 as either the male or the female parent.