Three firefighters were injured battling a two-alarm Upper East Side blaze this morning, authorities said.

The fire started about 7:30 a.m. on the second-floor of 797 Lexington Avenue, and spread to the fifth floor, according to an FDNY spokesman.

The flames were extinguished about 9 a.m.

One of the Bravest was rushed to New York Presbyterian Hospital in serious condition after fainting, but has stabilized, authorities said.

Two firefighters are also being treated there for minor injuries. “It was just a little smoke,” one said leaving the hospital.

“I woke up and there was a fire on the courtyard on the third-floor right outside my window,” said Julia Stack, 22. “[They] the flames were big. I had a moment when I was like, oh my God, what am I going to do?”

Her apartment suffered a lot of water damage, and was “completely unsalvageable,” she said.