Aki (安芸国; -no kuni) or Geishū (芸州) was a province in the Chugoku region of western Honshu, comprising the western part of what is today Hiroshima Prefecture, Japan.

In the Sengoku period it was the original seat of the Mori clan, until Mori Terumoto, one of the Council of five regents Toyotomi Hideyoshi appointed for his son, sided with Ishida Mitsunari before the Battle of Sekigahara and lost Aki and many of his other domains.