J.J. Watt is preparing to be a married man today!!!

J.J. and fiancee Kealia Ohai are getting hitched Saturday at a fancy hotel in the Bahamas, and lots of family and friends are on hand for the nuptials.

The couple was hanging at the hotel all week with their broods, hanging by the pool and celebrating during meals.

A big tent was erected Friday for the ceremony ... it's pretty extravagant -- a tent with chandeliers.

As TMZ Sports reported, J.J. and Kealia took out a marriage license this week in Harris County, Texas. They have exactly 90 days to seal the deal, but we're told that all goes down this evening.

J.J. and Kealia got engaged 9 months ago. They started dating 2 years ago.  BTW, Kealia is a soccer star who plays for the Chicago Red Stars.

Congrats!!!