Police said Saturday they arrested the manspreading jerk who slugged a woman in the face on a Brooklyn train.

Derek Smith, 56, of Brooklyn, was busted and charged with assault, officials said.

“This is amazing news and I’m relieved that he is unable to harm anyone else or retaliate against me,” relieved victim Sam Saia told The Post. “Excellent news!”

Saia, 37, was riding the N train through Bensonhurst while on her way to work in Manhattan when the man sat down and started overcrowding her around 7:45 a.m. Thursday.

“He proceeded to press me against the wall and man spread me excessively,” she wrote on Facebook after the incident.

“When I asked him to give me room, he yelled ‘B–ch, you ain’t nothing! I’ve raped white b–ches like you, f—ing c–t! You ain’t nothing, you f—ing b–ch!’”

When Saia tried to ignore him, he socked her in the mouth, bloodying her lip and knocking her head into the wall behind her, she said.

Smith was taken to Brooklyn’s Transit District 34 in Coney Island after the arrest.