WWE's Tammy Sytch -- Pinning Down Porn Deal ... '6-Figure Offer On Table'

WWE Hall of Famer Tammy Lynn Sytch ... aka "Sunny" ... could be doing an entirely different kind of rear-naked choke in the VERY near future -- 'cause she's thiiiiis close to signing a monster porn contract.

TMZ Sports has learned ... Sunny -- widely considered the very first "WWE Diva" -- has been in talks with Vivid Entertainment, the same company that produced Chyna's "Backdoor to Chyna" video.

Vivid tells us the two sides have spoken several times and a 6-figure offer is on the table for Sunny to become a "genuine porn star" -- not just a 1-time sex tape thing.

"After the tremendous success of Chyna, this makes total sense. Hoping we can work it out," Vivid honcho Steve Hirsch tells us.

We're told the deal is "VERY close" to being done ... and that Sunny is prepared to start shooting right away.

No word on what the first title would be ... but here are some suggestions:
-- "Piledrivin'"
-- "N.W.O-face"
-- "Monday Night Raw Dog"
-- "HummerSlam"
-- "D-Generation Triple-X"
-- "The People's Anal"