President-elect Donald Trump is fanning the flames of divisiveness amid the massive wildfires burning across Los Angeles ... posting a scathing critique of California Governor Gavin Newsom.

Trump hopped on his Truth Social platform Wednesday and placed the blame for the raging brush fires squarely at the feet of Newsom, accusing him of choosing an endangered fish over badly needed water resources to fight fires.

Trump kicked off his tongue-lashing by yet again referring to the gov as "Newscum" ... before  claiming Gavin "refused" to sign a declaration allowing water from Northern California to flow into the areas "currently burning in a virtually apocalyptic way." Trump said Newsom favored the Delta smelt fish over the people of California ... and that he would change all that once he takes office on January 20.

Meanwhile, actor James Woods -- one of the many celebs impacted by the out-of-control fires -- agrees with Trump that Newsom and L.A. Mayor Karen Bass are to blame for the natural disaster.

As many as 30,000 people have been evacuated due to fires around the L.A. area that broke out Tuesday -- including celebs living in the Pacific Palisades neighborhood, some of whom lost their homes -- Mandy Moore was also evacuated from her house overnight due to a different fire burning near Pasadena, and Whitney Cummings evacuated from the same area this morning. Two people have died in that fire -- their causes of death have not been released.

We've reached out to a rep for Gov. Newsom  ... so far, no word back.