Helen Cummings, who faced life imprisonment if convicted, was said to be "elated" after the jury unanimously found her not guilty on the ninth day of her trial in Florida.
The 33-year-old maternity nurse from Preston in Lancashire had told the court she thought her husband, Tyler Cummings, would kill her after she confronted him with pictures of him naked with another woman.
Mrs Cummings had told the court that she had feared for her life and had even contemplated suicide when she shot her husband on St Valentine's Day at their home in Fort Lauderdale.
The nurse, who is eight months pregnant with her late husband's child, said she that had found a loaded and cocked gun in a drawer in the house.
She told the court: "I went to the bedroom to see what was going on. He was on the bed. He sat up and he was coming towards me, like he lunged at me.
"His eyes were really fierce and I thought he was going to get me. It was either him or me."
The court heard she fired the .357 Ruger six times, with three bullets hitting her husband.Reuse content