Selena Gomez accidentally sold her iconic diamond “B” ring — yes, the exact one she posted when she went public with Benny Blanco — to multiple fans.

Here’s the situation … the singer officially kicked off her “12 Days of Really Rare Stuff” to celebrate her upcoming album with Benny, “I Said I Love You First.” As part of the promo, she’s selling a personal sentimental item each day.

Fans were blown away when they saw she was selling THE “B” ring for a mere $12 … especially after the custom Jacquie Aiche design was reported to be worth more than $3,000. Of course, multiple fans added it to their bag and checked out … and were naturally confused when they realized more than one had been sold.

We got to the bottom of it … and can confirm that Selena really did sell her own personal ring — to just one fan.

A source close to the “Only Murders in the Building” actress confirmed to TMZ there was a glitch on her website that allowed more than one person to purchase the ring.

Everything has been handled … the record label promptly informing some hopeful fans about the oopsie. They apologized and to make things right, are sending them some “fun items.”

Selenators have several more chances to lock down an exclusive item from their girl … the promo leads up to the album’s release on March 21.