The singer just slashed the price of her 20,000-square-foot mansion in Hendersonville, TN by more than a MILLION DOLLARS ... $1.25 mil to be exact.

Kelly originally listed the gorgeous 7-bedroom palace -- which she bought in 2012 -- for $8.75 mil in March 2017, but it's been relisted with a new $7.5 mil price tag.

The property sits on 4 acres right next to Old Hickory Lake ... just 25 miles from Nashville. It features a long, gated driveway that leads to a central fountain, and inside the front door is a double staircase leading to the grand foyer.

Along with the 7 beds -- including a master suite with a fireplace -- the 3-story house has 8 full bathrooms and 3 half baths. Other highlights include a saloon-themed bar with a pool table, a gym, a playroom with a ping pong table, a media room and a 2-story office ... with a private elevator.

And, that's just the inside. The backyard boasts a large saltwater pool, 2 spas, a garden, a greenhouse, a private dock and an area for outdoor dining. Of course, the home also comes with breathtaking views.