"Single Ladies" star Stacey Dash -- who starred in "Clueless" back in the day -- was hospitalized early Tuesday morning for "dehydration" ... this according to Stacey's rep.
Dash's rep tells us ... the 46-year-old actress was admitted to Encino Hospital in L.A. ... and she suspects it all stems from a meal she ate on Sunday night.
The rep tells us ... ever since that night, Dash "hadn't been able to hold down food or liquids ... not even water."
Dash was treated -- and hooked up to an IV bag -- but the actress has since been released from the hospital. Her rep says Stacey is currently "at home on bed rest trying to get stronger."