A Bronx man allegedly assaulted his ex-girlfriend and abducted her 1-year-old child after he sent a threatening message to the woman’s Facebook page, warning that he planned to kill her and her daughter.

Raheem Harris, 20, allegedly sneaked up behind the 20-year-old woman as she walked with her little girl along Morris Avenue in Claremont at about 5 p.m. Wednesday after he had fired off the angry Facebook missive.

He then allegedly punched his ex in the back of the head and grabbed the child.

Harris then allegedly ran with the child in his arms into nearby Claremont Park, where he abandoned the baby.

A passer-by heard the child weeping and discovered the tot in the woods, sources told The Post.

Harris, who has one prior arrest for robbery, was soon nabbed outside his home on Clay Avenue in The Bronx and charged with kidnapping, assault and reckless endangerment, the sources said.