Sources familiar with the situation tell TMZ ... the popular Halloween bash, hosted annually by founders George Clooney and Rande Gerber, is a no-go this year ... which is sure to upset the usual celeb-filled guest list.

We're told George and Rande will both be out of town the day the event is typically held -- which is normally the Friday before Halloween -- as the actor will be on set filming and RG will be away with wife Cindy Crawford, who is also a regular at the spooky soiree.

We're told Casamigos felt the party wouldn't be possible without the hosts ... who first held the bash back in 2018.

The party is typically held at the Beverly Hills mansion of Casamigos co-founder Mike Meldman and is known for bringing out the brightest stars in Hollywood, including Paris Hilton, Justin Timberlake, Rebel Wilson, Justin Bieber, Jessica Alba, Wiz Khalifa, Trevor Noah, Tyga, Taylor Lautner, Ryan Phillippe, Tobey Maguire, Paris Jackson, Robin Thicke and Josh Duhamel.

Last year's event saw Machine Gun Kelly and Megan Fox make a splash with a "Kill Bill" inspired costume. Austin Butler and Kaia Gerber also had a couple's costume to remember, dressing up as Andy Warhol and muse Edie Sedgwick.