Johnny Weir & Tara Lipinski -- REUNITING FOR KENTUCKY DERBY ... We're 'Fashion Experts' Now!

Johnny Weir and Tara Lipinski are teaming up AGAIN for the first time since Sochi ... and it's all to cover the Kentucky Derby for NBC as "fashion experts" ... TMZ Sports has learned.

Sources connected to the situation tell us ... NBC was so pumped up about how well Johnny and Tara were received during their Olympic coverage, the network has been gunning to get them back on the air together.

Now, we've learned the Peacock feels the Derby is the perfect situation -- and will have Johnny and Tara critique the famously over-the-top couture at Churchill Downs.