We study baryons and baryonic matter in holographic QCD using a D4/D8/(D8) over bar multi-D-brane system in the superstring theory. We obtain the chiral soliton solution for baryons in the four-dimensional meson theory derived from the multi-D-brane system. For the analysis of finite baryon-density matter, we investigate the chiral soliton on S-3 in holographic QCD, and find the delocalization of the soliton, i.e., the swelling of baryons in dense matter.