NBA star Donovan Mitchell says the refs straight-up "screwed" the Utah Jazz out of a win against Wednesday night the 76ers ... slamming the officiating as "f**king ridiculous."
The All-Star guard was booted from the game in the final minute of the Jazz's 131-123 loss to the Philadelphia in OT… after receiving two technical fouls for arguing with refs over calls.
Mitchell was LIVID as he headed to the locker room ... unleashing his frustrations on a nearby water cooler as he left the court.
After the game, Mitchell continued to blast the refs .