Matthew Fox had a rough 2011. After an arrest that May for a DUI, the 45-year-old “Lost” actor was slammed with accusations that he physically assaulted a woman in August.

Fox opened up about both experiences for the first time, during an appearance on the daytime talk show “Ellen.” In the show, which aired Wednesday, Fox talked about his embarrassment over the DUI, but said that he took full responsibility for the incident. And he said the alleged assault never took place.

TMZ identified the reported victim as Heather Bormann, the driver of a party bus Fox was a passenger on. Bormann alleged that she tried to prevent Fox from boarding the bus during a private party, because he was too drunk.

"He just kept staring at me with his mouth wide open and not saying anything,” Bormann told TMZ. “I told him, 'You have to leave, buddy. You are trespassing on my bus.”

It was at this point that Bormann claimed Fox leaned in and began punching her in the chest and groin. She claimed that she then punched the actor in his face, in an act of self-defense.

"I took one hand to his jaw and he was spitting blood. He stumbled backwards,” said Bormann.

But according to Fox, Bormann’s allegations are entirely false. He said Bormann was simply standing nearby when he got into a fight with another man, and invented the fight between her and Fox as a way to make some quick money.

“I was actually sucker-punched in the face by a man and I retaliated against the man that sucker punched me in the face," Fox said. "So a fight broke out and she was a woman that was in proximity to that and she decided that she was going to write up a different version of events that happened that night and try and extort money from me."

"It's difficult to be accused of something that you did not do,” he added of the ensuing legal cases. “I've never hit a woman in my life. Never have, never will. That's not a part of who I am as a man and hold that very dear to how I define my character. So that's been very difficult."

After Bormann’s case against Fox was dropped by Cleveland prosecutors, the actor had to go through civil proceedings and depose multiple witnesses. He added that he was speaking about it now for the first time because he was advised not to discuss the pending litigation at the time.

But Fox did own up to his DUI arrest, admitting that he had been drunk and saying that the event was a big wake up call for him.

“I grew up in a place where you had to drive 60 miles to go to town and hang out with your friends, so from a very early age that’s just what we did, and I lost friends in high school who were drinking and driving and had accidents on the highway, so I should have known better and yet I did that off and on throughout my life,” said the actor.

“Fortunately I didn’t hurt anybody – and then learned this lesson. … It’ll never happen again,” he said.