According to the invention, there is provided a novel soybean variety designated XB21Z06. This invention thus relates to the seeds of soybean variety XB21Z06, to the plants of soybean XB21Z06 to plant parts of soybean variety XB21Z06 and to methods for producing a soybean plant produced by crossing plants of the soybean variety XB21Z06 with another soybean plant, using XB21Z06 as either the male or the female parent.