According to a new lawsuit, obtained by TMZ, a woman named Giavanna Scotto claims she used to work as Matt's house manager at his Santa Monica estate a few years back, and she says complaints about sexual harassment at the hands of a fellow coworker fell on deaf ears.

In her suit, Scotto claims the sexual harassment started early in her tenure ... she says a male coworker aggressively grabbed her butt and breasts, and kissed her on the mouth multiple times ... all without her consent, she alleges.

What's more, Scotto claims the same coworker would bombard her with inappropriate text messages ... saying things like, "hello sweetheart," "miss you," "I miss you so much I love you I hope you are well I love you I love you," and "I love you how is our son."

She claims the coworker was undaunted by a lack of responses on her end ... and she says she "felt stalked."

In the docs, Scotto claims she complained to Matt and his wife, Agustina Picasso, about the alleged sexual assaults and harassment ... but she claims the couple "failed to take appropriate corrective actions" and that "Picasso clearly knew of the harassment and failed to act."

Scotto says the lack of action only emboldened her alleged harasser ... and she says he continued the same behavior until the end of her tenure and beyond. She alleges Matt and Agustina suddenly fired her in June 2022 without warning or cause.

Matt and his wife are being sued for failure to prevent sexual harassment and failure to prevent sexual assault and battery -- among other workplace violation causes of action.