Orlando Bloom is on the ultra high-profile guest list for Jeff Bezos and Lauren Sánchez‘s approaching wedding … and TMZ has learned the actor’s going stag amid rumors of his relationship with Katy Perry getting rocky.

Sources tell TMZ … OB plans to attend the days-long wedding celebration in Venice, Italy, taking place later this month … and Katy ain’t going to be by his side — but in this instance, there’s a perfectly logical explanation.

Katy is currently on tour in Australia, rockin’ 15 sold-out shows — and those dates overlap with the billionaire’s bash. And Katy’s tour was planned way before Jeff and Lauren locked in their lavish European nuptials.