The women's 100 metre freestyle competition at the 2018 Pan Pacific Swimming Championships took place on August 10 at the Tokyo Tatsumi International Swimming Center.

[1] The defending champion was Cate Campbell of Australia.

[2] Prior to this competition, the existing world and Pan Pacific records were as follows: All times are in minutes and seconds.

[3] Only two swimmers from each country may advance to the A or B final.

If a country does not qualify any swimmer to the A final, that same country may qualify up to three swimmers to the B final.