Elon Musk‘s first wife, Justine Wilson, says their marriage was super toxic … she claims he made her feel “insignificant” throughout their relationship — as if she was just his employee!

Justine said in the new “Musk” documentary … “I learned the term ‘gaslighting’ through my relationship with Elon.”

Elon’s first wife — who welcomed six kids with the Tesla CEO, including daughter Nevada, who died from SIDS at 10 weeks — claimed that he told her, “I am the alpha in this relationship,” as they danced at their wedding.

She added … “He was constantly remarking on the ways he found me lacking.”

Elon’s got a few exes dragging him in the new documentary, which premiered Tuesday at the Venice Film Festival.

Former flame Ashley St. Clair claims she turned down a $40 million NDA offer so she could participate in the doc.

She said she wanted to set an example for her kids that speaking truth to power doesn’t have a price tag.

However, the SpaceX founder called BS on her remarks.

Elon told us … “She was never offered that and has a history of making false claims.”