Octomom's Son -- I Need Protection from Crazy Ex-Nanny!

Octomom's oldest son claims his ex-nanny is bizarrely obsessed with him and won't leave him alone -- and he just got a restraining order to keep her away ... TMZ has learned.

According to legal docs ... Gina Bryson has been incessantly harassing 11-year-old Elijah Solomon with phone calls and text messages.

Sources close to Octo tell us, she fired Gina over the summer -- and that's when Gina allegedly began her campaign of psycho calls and texts.

The docs accuse Gina of leaking false stories about Elijah to the media -- including a story about him sexually molesting his younger sisters, and a story that he watches porn.

A judge has prohibited Gina from going within 100 yards of Elijah, or contacting him in any way.