Laura Dern Divorce Final -- No Going Back Now ...

The fat lady has sung in Laura Dern's divorce ... after a failed attempt at reconciliation, the actress' divorce from singer Ben Harper has been finalized.

TMZ broke the story ... Harper blindsided Dern with divorce papers back in 2010 after 5 years of marriage and two children ... but in 2012, before it was finalized, the two tried to get back together.

The reconciliation was a colossal failure ... and months later, Dern decided she wanted out for good, filing her response to Harper’s divorce petition, demanding primary physical custody of their kids.

Now, a year later, it's all over ... a judge has signed the divorce petition, meaning Laura and Ben are officially single.

The terms of the settlement are confidential. Sources connected with the couple tell TMZ ... the couple will have joint custody, although Laura will have the kids more than Ben. We're also told she will get "minimal" child support. We're told neither party will get spousal support.

Another one bites the dust.