The former US Navy SEAL who fatally shot Osama bin Laden has only one regret: the al Qaeda monster he killed with three shots to the head was buried at sea. “I would have hung him from a bridge in New York City,” and let the locals deal with him, Robert O’Neill told The Post. Here the retired Team Six member offers The Post’s David Spector a riveting blow-by-blow account of Operation Neptune Spear, which unfolded 15 years ago today at bin Laden’s secret compound in Abbottabad, Pakistan. He also reveals the heroic operators’ 9/11 motivations. “We were going for the single mom who dropped her kids off at school on a Tuesday morning, then an hour later . . . jumped out of the World Trade Center, pressing down her skirt as her last act of human decency. She was never supposed to do that.”

We first found out about the top-secret mission three weeks before it was executed. The first thing they said was, “This is not a drill, this is real.”

All they told us was we found a thing in a house in a bowl in this mountain range, and you’re going to go get this thing and bring it back. What is this thing? Well, we can’t tell you. Which country? Can’t tell you. How are we getting there? Can’t tell you. How much air support? None.

Hearing that was actually a relief because that was our first answer.

They said on a Friday, go home and be with your kids, and come back Sunday for a read-in. I asked, “Who’s going to be at the read-in?” It was the vice president, the secretary of defense, the secretary of the Navy.

We’re like, “What in the world?”

The read-in was in a room behind armed guards at the Cherry Point Marine Corps Air Station in North Carolina. The SEALs were told, “This is as close as we’ve come to Osama Bin Laden.”

We came up with the perfect plan and rehearsed it day and night on mockups of the exterior of Bin Laden’s house. We were introduced to some Sikorsky UH-60 Black Hawk helicopters that I don’t think even President Obama knew about. Helicopters would pick us up; We’d drop down on ropes and land on the roof.

We’d practice different scenarios: what if a car leaves, what if we get separated, what if we’re trapped outside? My experience in Iraq was the ultimate preparation. In training, you might talk about it and forget it, but when somebody gets shot, that’s written in blood.

One day my boss asks, “What is the worst thing that could go wrong?” The youngest guy said, “The helicopter could crash on bin Laden’s front yard.” We looked at him like, “Why did you jinx us?” Sure enough, that’s what happened.

In the world of special operations, a casual worry isn’t just a jinx — it can be a blueprint for how to handle chaos.

This would be a one-way mission. You’re not afraid you’re gonna die, but you’re prepared for death. We had the four best pilots in the world, but they’d only flown these choppers for maybe a week. One of the younger guys pulled me aside and said, “Don’t get this wrong, I’m definitely going, but if we know we’re going to die, can we discuss why we’re going?”

We all talked about it. We weren’t going for the fame or the reward. We were going after bin Laden for the first Americans who were forced to fight al Qaeda, to the death, toe to toe, on a Tuesday morning: the passengers on Flight 93.

You knew that any one of us could pull ourselves out and live for another 50 years. But when you’re on your deathbed, if you could give every single day back for one shot at this motherf–ker . . .

The hardest part is telling your kids goodbye, because death is coming. The day I shipped off, my 3-year-old daughter packed a Hello Kitty suitcase and said, “When you get home, you’re taking me on vacation.” I had to rip the scab off, give her a kiss and look her in the eyes one last time, fully believing I wasn’t going to come back. That’s the hard part. My poor [former] wife had no idea where I was going.

We waited at a base in Jalalabad, Afghanistan, for a green light. There was another SEAL team there who didn’t get the mission because if they changed their behaviors, it might tip the enemy off.

We finally got the green light.

We wanted zero percent illumination. We wanted it completely dark because we’re good in the dark. We went on Sunday. We don’t know if our stealth technology works; it’s a 90-minute flight into Abbottabad, and Pakistan could shoot us down.

The lead CIA analyst who found bin Laden was this badass, no-nonsense woman. She walked us through how she found him and what we could expect when we got to his compound in minute detail. We knew there would be a gunfight — if anybody is going to martyr his entire family, it’s bin Laden.

If we got caught, I had one rule: I was saving one bullet for myself. I’m not going to a Pakistani prison. There was some concern that the Pakistani police would arrive. We told the White House we didn’t want to kill any beat cops.

We were told President Obama said to [then-three-star Admiral William] McRaven, “How much firepower do you need to rain hell on Pakistan? My men are not surrendering to the Pakistani police.”

That was some old school Chicago hardball politics right there.

The whole thing happened in the span of nine minutes. We landed at 12:30 a.m. The first helicopter went down. We knew something happened and we decided to get out and figure it out.

I remember looking up over a 20-foot wall, seeing the top of bin Laden’s house. I remember thinking calmly, “Well, I guess we start the war from here.” Off to my left, there’s a double door. Another SEAL put a 7-foot charge on the door to blast it. He blasted the door, it opened, but there was another brick wall behind it. “S–t, that’s a fake door,” I thought. He’s in there.

We had to cross the front of his house. We were going to blast the garage open, but before we could, it opened and a glove I recognized gave me a thumbs up. I walk past the guys in the garage wearing American flag patches, thinking “Who the f–k are these guys?” They’re the pilots from the other helicopter that went down.

We get into the house and there’s a long hallway. The first thing I did was hop into the room on the right. Nobody said a word. We work quiet and read off each other. We think there should be bombs in the house. I see guys ahead of me moving children to safety.

Down the long hallway there was a stairwell. The CIA analyst said [Osama’s brother] Khalid Bin Laden would definitely be on it and if you can ace him, you get a shot at the big guy. One of my friends is trying to breach a barricaded door. The door blows and we go up. Khalid is there, just like the woman said. The guy in front whispered “Come here” to him in Arabic and Urdu. It confused him; he came out with his gun and got blasted.

We got to the second floor. Everyone split off to clear rooms. A SEAL is pointing to the last set of stairs. On top of the stairs is a curtain where the door should be. I went up with him as the number two man. He saw people moving behind the curtain. We thought they were suicide bombers. I look down at my shoes and I remember thinking, “Okay, I’m going to blow up now, I’m going to see what that feels like, and I’m tired of thinking about it. Let’s go.”

We went through that curtain and he moved them out of the way. They turned out to be Bin Laden’s wives.

He turned left and I turned right and there was bin Laden standing there, three feet away.

I recognized him immediately. I was impressed with how skinny he was. His beard was sort of gray. His hands were on his wife Amal’s shoulders. I took it as a threat; he could blow himself up.

At SEAL Team Six, we shoot you twice in the head right away. I shot him twice and shot him again with my H&K 416. He crumpled on the foot of his bed.

I just shot Bin Laden — like what the f–k? Everything I had ever known, everything I planned, just changed drastically.

Now I know I need to move Amal back and shield her with my body because other guys are coming in. As I’m moving her, his 2-year-old son Hussain was standing there. We’re all fathers. My thought was, “Why did he have to see this?” I move him back and then I turn around.

Our rules are, if you kill it you own it. I have to clean his face, hold his head together and take a picture. One of my guys asks, “Hey, are you good bro?” I said, “Yes, what do we do now?” He said go find the computers.

“You just killed Osama bin Laden, your life is about to f–king change, now get back to work,” he told me.

That snaps me out of it.

We didn’t blow up. We might make it home.

I ran into [fellow SEAL and the team’s dog handler] Will Chesney. I told him, “I think I just shot that f–ker in the face.” We hear on the radio “For God and country, Geronimo, Geronimo, Geronimo.” Geronimo was the code word to signify bin Laden had been killed. We high-fived.

We found offices, computer towers, floppy discs and CDs. They sent two guys out to blow up the crashed helicopter. I went back to the third floor; they already put bin Laden in the body bag. Everyone’s starting to realize we might see our homes again. We get in the helicopter.

Now we gotta live for 90 minutes. If I make it that long, I get to see my kids again.

Pakistan definitely scrambled F-16s. . . . Ten minutes go by, then 20, now it’s 30. You can hear the helicopter really picking up speed. We hit 60 minutes. S–t, it’s been 80 minutes. All we had to do is cross into Afghanistan and we live.

The pilot came on the radio and said, in his monotone voice, “All right gentleman, for the first time in your lives, you’re going to be happy to hear this: Welcome to Afghanistan.”