The women's 100 metre freestyle competition at the 1999 Pan Pacific Swimming Championships took place on August 26–27 at the Sydney International Aquatic Centre.

[1] The last champion was Jenny Thompson of US.

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

The first round was held on August 26.

[1] The final was held on August 27.