A Lower East Side resident was beaten, slashed and robbed of his designer watch when he confronted a man whom he found with his girlfriend, cops said. 

The 33-year-old victim had just gotten home around 7:10 p.m. June 6 when he found the stranger with his gal pal at his apartment at Delancey Street and Baruch Drive, police said late Wednesday. 

The two men got into a fight that ended with the intruder punching the victim in the face multiple times and slashing him in the neck, authorities said. 

The suspect also swiped his $7,000 Cartier watch and keys before bolting, cops said. 

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

Police released a surveillance image of the suspect, who remains at large.