A stranger with a face tattoo slashed a straphanger during a clash inside a Midtown subway station early Friday, cops and sources said.

The 35-year-old commuter got into a dispute with the attacker just before 1 a.m. inside the 49th Street station – prompting the brute to slash him across the neck with a “cutting instrument,” police said.

The wounded victim got on a southbound Q train and took it to 34th Street-Herald Square, where he flagged down cops on a foot post, authorities said.

The victim was taken to Bellevue Hospital, where he was listed in stable condition, police said.

The two men did not know each other, but it was unclear what sparked the brawl, law enforcement sources said.

The assailant, who fled on foot, is described as a man with a dark complexion, ponytail and face tattoo, last seen wearing white sneakers and carrying a black backpack, according to authorities.

He had not been caught several hours later.