South African athlete Oscar Pistorius has been found guilty of culpable homicide after the judge found he killed his girlfriend by mistake.
Judge Thokozile Masipa said the athlete had acted "negligently" when he fired shots through a toilet door, but in the "belief that there was an intruder".
She said the state had failed to prove he intended to kill Reeva Steenkamp.
The judge allowed Pistorius to remain on bail ahead of sentencing which is to take place on 13 October.
The victim's parents, June and Barry Steenkamp, condemned the verdict, saying it was "not justice for Reeva".
Speaking in an interview with NBC News, June Steenkamp said: "He shot through the door and I can't believe that they believe it was an accident."
However Arnold Pistorius, the athlete's uncle, said the family was "deeply grateful" to the judge for finding him not guilty of murder and that a "big burden" had been lifted.
"There are no victors in this," he added. "We as a family remain deeply affected by the devastating, tragic event... It won't bring Reeva back but our hearts still go out for her family and friends."
South Africa's prosecuting authority said it was "disappointed" Pistorius was not convicted of murder but said it would wait until after sentencing to decide whether to appeal.
The verdict leaves the disgraced sprinter facing up to 15 years in jail, although the judge could suspend the sentence or only impose a fine.
The BBC's Nomsa Maseko said there was a poignant moment in court when Oscar Pistorius's father and Reeva Steenkamp's father hugged each other as the judge adjourned to consider bail.
The athlete was also found guilty on a charge of negligently handling a firearm that went off in a restaurant.
At the scene: Pumza Fihlani, BBC News
Oscar Pistorius was a picture of composure as the judge announced he was guilty of culpable homicide, a lesser count of murder in South Africa.
The athlete, who became emotional on Thursday after being described as an "evasive witness", seemed to have been expecting this verdict. The judge had already spoken of his negligence and use of "excessive force" when he fired through the door.
Some say this verdict is the best outcome he could have hoped for.
Many South Africans have questioned the judge's decision to acquit him of murder and argue that the prosecution may have grounds to appeal.
For now, the Pistorius family seem relieved. But in the benches opposite them, friends and relatives of model Reeva Steenkamp wept, while others, including her mother June, seemed shell-shocked.
Mr Pistorius said he and Ms Steenkamp had dinner at about 19:00 before going to bed at 21:00. He said he woke in the early hours, spoke briefly to his girlfriend and got up to close the sliding door and curtains.
Judge Thokozile Masipa questioned the reliability of several witnesses who said they heard screams and gunshots between about 03:12 and 03:17, saying most had 'got facts wrong'.
Mr Pistorius said he heard the bathroom window sliding open and believed that an intruder, or intruders, had entered the bathroom through a window which was not fitted with burglar bars.
Mr Pistorius said he grabbed his firearm and told Ms Steenkamp, who he thought was still in bed, to call the police.
The judge said it made no sense that Ms Steenkamp did not hear him scream 'Get out' or call the police, as she had her mobile phone with her.
Mr Pistorius could see the bathroom window was open and toilet door closed. He said he did not know whether the intruders were outside on a ladder or in the toilet.
He had his firearm in front of him, he heard a movement inside the toilet and thought whoever was inside was coming out to attack him.
'Before I knew it, I had fired four shots at the door,' he said.
The judge said she did not accept that Mr Pistorius fired the gun by accident or before he knew what was happening. She said he had armed himself with a lethal weapon and clearly wanted to use it. The other question, she said, was why he fired not one, but four shots before he ran back to the room to try to find Ms Steenkamp.
Mr Pistorius said he went back to the bedroom and noticed that Ms Steenkamp was not there.
Mr Pistorius said this was when he realised she could have been in the toilet and rushed back to the bathroom.
Mr Pistorius said he screamed for help and went back to the bathroom where he found the toilet was locked. He returned to the bedroom, pulled on his prosthetic legs and turned on the lights before bashing in the toilet door with a cricket bat.
When the door panel broke, he found the key and unlocked the door and found Ms Steenkamp slumped on the floor with her head on the toilet bowl. He then carried her downstairs, where he was met by neighbours.
The double amputee had denied murdering Ms Steenkamp after a row on Valentine's Day last year, saying he shot her by mistake.
With this the judge agreed, saying "it cannot be said that the accused did not entertain a genuine belief that there was an intruder".
But she said: "The accused knew there was a person behind the toilet door, he chose to use a firearm.
"I am of the view the accused acted too hastily and used too much force. It is clear his conduct is negligent."
Pistorius was convicted on an unrelated firearms charge - negligently handling a firearm that went off in a crowded restaurant.
He was acquitted of another charge of firing a gun in public, through the sunroof of a car, and of a charge of illegal possession of ammunition in the home where he killed Ms Steenkamp.