The women's 100 metre butterfly S12 event at the 2012 Paralympic Games took place on 2 September, at the London Aquatics Centre in the Olympic Park, London.

The event was for athletes included in the S12 classification, which is for competitors with visual impairments.

[1] Eight swimmers took part, representing a total of seven different nations.

Poland's Joanna Mendak won the gold medal.

Eight swimmers were involved in the competition which progressed directly to a final with no heats contested.