Evan Rachel Wood -- The Merkin Tale

Evan Rachel Wood is getting all sorts of buzz for a special wig she had to rock for an upcoming HBO project ... a wig that was custom built for her crotch.

The "True Blood" star is slated to go full frontal in the HBO miniseries "Mildred Pierce" -- and at a recent NY press event explained, "Let’s just say, I had to wear a wig because it was in the 30s, and everything had to look like it was in the 30s."

According to Wood, her co-star Kate Winslet encouraged her to do it -- “I looked at Kate and she was like, ‘You’ve got to do it. Trust me, it’s so brave. Put a merkin on and you’ll be fine.”