was a town located in Mitsugi District, Hiroshima Prefecture, Japan. As of 2003, the town had an estimated population of 16,283 and a density of 884.95 persons per km². The total area was 18.40 km². On March 28, 2005, Mukaishima, along with the town of Mitsugi (also from Mitsugi District), was merged into the expanded city of Onomichi.