Ron White's pending divorce just took another major twist -- because he says his so-called estranged wife isn't really his wife, anyway.

According to docs filed by Ron ... Margo Rey's divorce filing last month was totally bogus, because she was never legally married to him. Although they had a wedding ceremony in October 2013, White says they never got a marriage license.

As for Margo claiming they had a common law marriage in Texas -- Ron calls BS in the docs ... saying they never lived together there as husband and wife and "never represented to others that they were married."

He's also quick to point out there's no common law marriage in Cali ... so he wants the whole divorce tossed outta court. 

We reached out to Margo ... no word back so far.