Here's the deal ... the entertainment mogul received the honor of a massive portrait of herself that's going into the Smithsonian National Portrait Gallery in Washington, D.C. The unveiling went down Wednesday morning, with Oprah's friends and family in attendance.

Shawn Michael Warren is the artist, and he joined O to pull off the drape covering his work, which looks to stand at about 7 feet tall or so. Keep in mind, Oprah had never seen the finished product.

Once the curtain was yanked ... she could see the painting in all its glory, depicting her in a purple dress, smiling wide in her "prayer garden." To us, the portrait looks fantastic, and most everyone there seemed to agree too ... but it's hard to tell if Oprah liked it.

Maybe we're reading too much into how she reacted, but she certainly looked shocked. It's just not clear if it's a look of stunned joy, or astonished mortification. 😅

We'd like to assume it's the former, and that she digs it ... because honestly, it is quite nice.

Anyway, this thing is permanently the museum's forever -- and like we mentioned, O is joining an exclusive club ... especially as it pertains to modern celebs. The Smithsonian features portraits of tons of famous figures throughout history, but only a handful of 21st-century celebs ... not including presidents, like Barack Obama, who has one.