An elderly man was clinging to life last night after a motorist plowed into him on the Upper East Side and fled the scene, police said.

The 85-year-old was crossing First Avenue at 84th Street at 5 p.m. when a gold Nissan Maxima slammed into him and took off.

The victim was rushed to New York Hospital and was in critical condition, police said.

Witnesses called it a “nasty” collision.

“There were a lot of people standing around the man’s body. It looked like a nasty accident. He wasn’t moving,” said Rogelio Martin, 65.

He added that the intersection is dangerous.

“Cars really speed down First Avenue — it’s not a surprise,” he said.