Sammy Hagar 's annual Birthday Bash went full-on wild at Cabo Wabo Cantina last night, with rock royalty, surprise guests, and tequila flowing like... well, tequila!

The icon's energy is unreal in this video -- the 77-year-old's onstage was having a blast while delivering a powerhouse version of Man in the Box that had fans losing it.

Even pop icon Belinda Carlisle stole the show for a moment, hitting the stage to belt out "We Got the Beat," twirling and dancing with Sammy like they were teens all over again!

Belinda was also spotted watched from the VIP platform, dancing and singing along to "Why Can’t This Be Love" while a lucky Van Halen superfan got invited onstage to shred "5150" and "Summer Nights.:

Of course, the night was fueled by plenty of Santo Tequila -- Sammy’s col

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