A grieving mother collapsed in a Manhattan courtroom — sobbing, “I need my son,” during the emotional sentencing of her son’s killer today.

Omar Gaspar was only 19 and a promising new boxer when he was stabbed in the chest last October by Exequiel Reyes, 23, of Manhattan, during an argument after a party on East 75th Street.

Reyes had pleaded guilty to manslaughter in June; today, he remained silent as he was sentenced by Manhattan Supreme Court Justice Thomas Farber to 16 years prison.

“My son was about to have his first fight this year,” Gaspar’s mother, Luisa, 43, cried while making a statement to the judge about her grief.

“Then some crazy man came and took his life away.” Family members said Gaspar, who trained in Lower Manhattan, had been about to begin training at the prestigious Wild Card Boxing Gym in LA.