Exclusive

William Shatner wants Scotty the judge to beam him up and out of his marriage, 'cause he's calling it quits after 18 years ... TMZ has learned.

The 'Star Trek' actor just filed for divorce against his wife, Elizabeth, whom he got hitched with back in 2001. Sources familiar with the matter tell us Bill and Liz's split should move along relatively smoothly, as we're told the couple has a prenup.

Our sources say the Shatners are still negotiating the financial terms -- but one thing won't be an issue ... spousal support. We're told, per the terms of the prenup, neither party will receive any support from the other.

Of course, William and Elizabeth don't have any kids ... so no issues there. We're told divorce docs could soon be submitted for a final signature from a judge. It's almost a done deal at this point.

Elizabeth is Will's fourth wife -- he was previously married to Nerine Kidd, Marcy Lafferty and Gloria Rand ... and only had children with Rand. It's Elizabeth's second go-around ... she was married to Michael Glenn Martin before William. He's 88 ... she's 61.

Disso Queen Laura Wasser is repping WS in the divorce. She's on a nice little roll right now -- Laura Dern just picked up a Golden Globe nom for portraying her in "Marriage Story."

BTW ... Shatner's worth an estimated $100 million.