Celeb Stylist Irene Albright -- Hey, Hollywood ... Come Get Glammed Up in My Mansion!

Stylist Irene Albright is running the world's largest changing room -- it's a mansion in the Hollywood Hills ... where celebs have been coming and going just to get dolled up for award season.

Sources tell TMZ … Albright has opened up shop inside the huge master bedroom of a 4,200-square-foot home she's renting for $25K a month! We're told she has more than $3 million worth of dresses on racks.

The 5-bed, 6-bath pad was designed by Andrew Gulyas ... who's also a huge celeb real estate agent in town.

As for who's been dropping by to pick up dresses -- Albright tries to keep that under wraps, but we know she's styled for Demi Moore, Meryl Streep and Katie Holmes in the past.