A Brooklyn man is clinging to life after an early-morning fire swept through his Greenpoint apartment yesterday, cops said.

The unidentified man, in his 30s, was critically hurt in the 3 a.m. blaze, which sent residents of the smoke-filled Dupont Street building into a panic.

Neighbors said that the man lives there with his girlfriend, who wasn’t home at the time, and that the couple’s cat died in the fire.