Serial-killing Mafia snitch Sammy Gravano says he once plotted the ultimate hit — against mob boss John Gotti.

The city Mafia turncoat, in his first videotaped interview since 1997, said he thought about murdering the powerful head of the Gambino crime family because Gotti was trying to get him to take the fall for him with the feds.

“I start thinking, ‘Where we’re gonna kill him, who’s gonna drive him, where we’re gonna bury him, who do I have to kill: his brother, son, this one, that one, Genie Gotti.’ I happened to like Genie Gotti,’’ Gravano told YouTube interviewer Patrick Bet-David, referring to the Dapper Don’s brother, Gene.

“At one point, there was 14, 15 people on a piece of paper,’’ Gravano said of his hit list. Then “I ripped it up and flushed it down the bowl.

“Here’s my best f–king friend, my boss,’’ the turncoat said of John Gotti — who he eventually ratted out, paving the way for a life sentence for the Mafia chief, who died in prison in 2002.

“I did so many things for this guy. I rigged the trials, I threatened people, I f–king bribed people, and he turns on me,” raged The Bull, who claimed in the interview that Gotti told him he needed to be his “sacrificial lamb’’ and fall on his sword with the feds so the boss could escape charges.

“I was betrayed by someone who’s a brother, a father, somebody you gave your whole life to,” Gravano said.

“When the rubber meets the road, he’s throwing you to the wolves. It broke my heart, it broke me,” he said.

Gravano said he thought, “F–k him, f–k the mob, I don’t give a f–k if I get killed.”

But in the end, “I just walked away.”