Kelly Clarkson Abruptly Cancels Start to her Vegas Residency

Kelly Clarkson fans likely never imagined a moment like this -- the Grammy winner canceled the opening show for her Las Vegas residency just 90 minutes before it was supposed to start.

KC broke the news on Instagram Friday night and blamed the shocking cancellation on her voice ... saying she needed time to rest because the residency prep and rehearsal took a "toll" on it -- and she wants everything to be "perfect" for her dedicated fans.

She added ... "We have been working 24/7 to make Studio Sessions the most intimate and extraordinary experience with and for my incredible fans. I am beyond grateful that you always show up for me and I am devastated to have to postpone tonight and tomorrow’s opening at Caesars."

The "American Idol" alum confirmed she will hit the stage next weekend -- so folks hoping to catch her Saturday show are also outta luck.

She did not reveal if the affected shows will be rescheduled. TMZ reached out to her rep for clarification ... but so far, no word back.

The "Breakaway" singer announced her Las Vegas residency at the Colosseum at Caesars Palace in February ... just before she caused concern by going MIA from her talk show.

She has dates scheduled through through mid-November.