Imagine Dragons frontman Dan Reynolds nearly took a nasty tumble ... almost wiping out while sprinting through the crowd during the band's performance ... and it's all on video.

The singer was performing shirtless Thursday night at Yaamava' Resort & Casino's 40th anniversary celebration in Highland, CA ... when he suddenly hopped off the stage and took off running into the crowd.

Dan appeared to lose his footing in the aisle, stumbling forward and coming within inches of bowling over an usher before catching himself at the last second.

It all happened in the blink of an eye ... Dan quickly regained his balance, never stopped singing, and kept charging through the crowd like nothing happened.

The near face-plant didn't put a dent in the show's energy, either. Fans cheered him on as he brushed off the close call and finished the high octane performance without missing a beat. The singer, who's been dating actress Minka Kelly since 2022, never let the stumble slow him down.

Imagine Dragons' performance followed a Christina Aguilera gig earlier in the week ... and Snoop Dogg is set to put on a show Friday night.