'Masked Singer' Date Night Includes Taylor Swift Connection

It's date night on "The Masked Singer" ... and we've learned one of Taylor Swift's "close friends" might be under one of the costumes!!!

The celebs on the eccentric singing competition are revealing personal information about their love lives in the Wednesday date night episodes on FOX ... and here's where we get our Taylor connection.

Production sources tell TMZ ... one of Wednesday's performers has been seen together with the "Look What You Made Me Do" singer.

So, the obvious question is ... who in Taylor's inner circle is rocking the mic behind the mask?!?

There's a ton of possibilities, and some huge names, because Taylor has been out with a bunch of famous hunks over the years ... like Harry Styles, Jake Gyllenhaal, Taylor Lautner, John Mayer, Joe Jonas and Zac Efron ... just to name a few.

But, it may not be an ex. One source with direct knowledge tells TMZ ... the person behind the mask also collaborated with Taylor on a project.