Sharon Osbourne's very grateful a fan returned her massive diamond ring ... and, it clearly pays to be honest -- 'cause she's offering that fan a once-in-a-lifetime experience.
Here's the deal ... Osbourne revealed to her Instagram followers she lost her wedding ring at a Birmingham event for soccer team Aston Villa's new store -- but, luckily, a Good Samaritan found it and chased her down in the parking lot to return it.
At the time, Sharon explains, she was so shocked, she didn't get the fan's name ... and asked fans for help identifying her guardian angel 'cause losing her wedding ring -- her second, after the original was stolen -- would've been really unfortunate.
Welp, internet sleuths remain undefeated ... 'cause they identified her as Sharon Bardsley -- a local business owner and mother who was at the opening with her 15-year-old son.
Now, Sharon's repaying Bardsley's random act of kindness ... telling TMZ she's offering Bardsley and her family a VIP experience at a show her husband Ozzy Osbourne's participating in next year.
He's preparing to perform in Aston -- an area of Birmingham where he grew up -- sometime next year with a number of friends, we're told ... and, Bardsley and her loved ones will get to watch the whole show from the wings.
Osbourne's already reached out to Bardsley ... the two having a lovely conversation on the phone yesterday.
Moral of the story ... keep an eye on the ground -- ya never know which celeb's jewelry might be lying there!