The victim, a 49-year-old man, was found outside a pub in Widnes at about 3.20pm on Sunday, police said.
He had serious stab wounds and died before he could be taken to hospital.
A second man, 35, and a woman, 39, have been arrested in connection with the stabbing and remain in police custody.
Chief Inspector Simon Parsonage said he understood the community would be "concerned about what has happened".
He added: "I would like to reassure those living locally that we are doing everything we can to establish the circumstances of what has happened and extra officers will be patrolling the area overnight and into the morning to provide reassurance."
Meanwhile, a young man was stabbed in the London area of Tottenham on Sunday afternoon.
Police were called just after 2pm to Seven Sisters Road at the junction with St Ann's Road.
They found a man, 25, who had been stabbed a number of times.
His injuries were described as life-changing.
No arrests have been made.