​A 25-year-old man ​wished “Happy New Year” to a woman just before he saved her life by shoving her from a faulty elevator that suddenly took a plunge — but the brave act cost him his own life, witnesses said.

Stephen Hewett-Brown, 25, was in the crowded elevator at 131 Broome St. ​on Manhattan’s Lower East Side ​when Erudi Sanchez, 43, who lives in the building, ste​​pped inside around 11:45 p.m. with her 10-year-old nephew to throw out trash.

“When I got into the elevator, I felt it dropping and I thought my feet would get caught in the gap but the man pushed me out and said, ‘Happy New Year,’” Sanchez told The Post on Friday in Spanish.

But suddenly, the malfunctioning ​elevator dropped farther and Brown’s body was caught between ​it and the third floor, Sanchez said.

“I saw he was trapped and the elevator was crushing him. It was awful,” she said.

The woman’s son-in-law Emanuel Coronado, 23, desperately tried to pull Brown out, but it was too late.

“I feel bad I couldn’t save him. I tried to pull him out but the weight of the elevator was too heavy,” said Coronado, who was still shaken up by the horrific accident.

He said a woman in the elevator who appeared to be with Brown was in hysterics as she witnessed him being mangled.

“She was crying. He was saying, ‘I can’t breathe. Please help me,’” Coronado recalled.

​“To me, he is a hero. My mother-in-law might not be alive right now.”

A witness told The Post that ​Hewett-Brown and the other people in the elevator​, except for Sanchez,​ were dressed up and headed to a New Year’s Eve party on the 15th floor.

FDNY officials said a 911 call​ came in​ at 11:54 p.m. — and ​emergency responders were on the scene just five minutes later.

“It was a tragic call, a very unfortunate incident,” said an FDNY spokesman.

Sanchez was grateful for Brown’s selfless last act.

“He did a very valiant act to save me. We want to thank him and his family and pray that God gives them peace and comfort. It’s something I’ll never forget,” she said.

The traumatized woman also said the building is known to have issues with the elevators.

“They don’t do a good job repairing them. Two months ago we got stuck inside and had to press the alarm button and were rescued after 15 minutes,” she said.

Numerous complaints about elevators at the building have been filed with the city Department of Buildings​, some as recently as June 22, according to records.

Meanwhile, friends and family of Brown were ​in mourning Friday at his Eastchester home.

“I’m grieving my son. We don’t want to say anything,” Brown’s mom told reporters at their Eastchester home.

Brown — who went by the ​nickname​name StevOD — frequently posted his own written and recorded rap songs on SoundCloud and was working on an EP album, according to social media.

Ejiro Omenih, 22, said he wasn’t surprised to hear of his close pal’s heroic act.

“That’s the kind of heart he had. He’s always been like that, very responsible, caring about other people,” said Omenih through tears.

“He’s the head of the family. He has been the breadwinner for years, taking care of his grandmother, his mother, younger sister and a younger brother, Chris.”

Additional reporting by CJ Sullivan, Emily Saul and Shawn Cohen