The 21-year-old singer sent a note to fans in a Twitter message this afternoon saying, "Louisville, I so sorry to have to postpone this show to Oct 11. This is my first time having to do this. I'm so, so sorry."
An announcement on her official web site notes the cancellation is necessary for health reasons but did not elaborate: "Due to illness and under doctor's orders, Taylor Swift has been forced to postpone tonight's performance, and the show has been rescheduled."
Her next stop is scheduled for July 8 in Charlotte, N.C.