KTDY (99.9 FM) is an adult contemporary music formatted radio station in the Lafayette/Acadiana market in Louisiana, United States, owned by Townsquare Media.

In the early 1970s, due to Federal Communications Commission (FCC) regulations discouraging full AM/FM simulcasts, KPEL-FM began programming a Progressive Rock format in the overnight hours, retaining the beautiful music format during the day.

Eventually, KPEL-FM changed its calls to KTDY in early 1977, and the progressive format was expanded to broadcast the entire day.

KTDY at one point aired American Top 40 with Casey Kasem, King Biscuit Flower Hour, The Record Report and The Special Of The Week with Robert W. Morgan, Scan, Powerline, Earth News, Dr. Demento, Off The Record with Mary Turner, 60 Second LP, and in the early days of the station a strange daily comedy serial called Kremmin of the Star Corps which turns out was created by well known BBC Radio 1's on air personality Kenny Everett.

The afternoon show was hosted by JayCee, who in 2013 was tagged by The American Lung Association as Southwest Regional's "Volunteer of the Year", until his departure in early 2023.