An investment banker jumped to his death from the window of his million-dollar apartment in the Financial District on Thursday, sources and authorities said.

The 29-year-old man plunged from the 24th floor of the luxury Ocean apartment building at 1 West St. at about 10:40 a.m. and landed on a guardrail near the northbound Battery Park Underpass, narrowly missing a black SUV.

The man’s body was mangled by the impact, leaving one of the vehicle’s passengers horrified, witnesses said.

“I went outside, and the woman in the car was screaming, ‘I didn’t know where he came from!’ ” said Hans Peler, 48, a manager at the building’s parking garage.

“It happened right in front of our guy who waves cars in with the flag. He was so shaken up, I told him to go home.”

The gruesome aftermath sent tourists on an open-air bus that was stuck in traffic scrambling for their cellphones to snap pictures of the body, said workers at the building.

“The head hit the railing . . . Half his head is on one side of the railing, half on the other,” recalled Frank Rodriguez, 44, a handyman who was working nearby. “It’s never worth this . . . Life is too precious.”

Sources said the young banker had made several attempts to kill himself earlier in the morning, including cutting his wrists, before making the plunge.

The man — whom police did not immediately identify — was from a wealthy family in Westchester County, sources said.

He had apparently become very successful on his own.

He owned his apartment in the 36-story Ocean complex, which overlooks The Battery and New York Harbor, and had just returned from a vacation in the Bahamas, sources said.