The Las Vegas Review-Journal reported that the man and woman were found Friday when police arrived for a welfare check at the room at Circus Circus.
Each person had been stabbed multiple times. Their names were not immediately released.
Metropolitan Police Department Lt. Ray Spencer said investigators have not yet determined whether it was a murder-suicide. But he said the early indication "leans toward" that possibility.
The newspaper said a person reported hearing an argument coming from the room the previous night.
Police said there is no active threat to guest safety at the hotel.