Pistorius is now set to go back to jail after he was released on parole in October having served one year of his five-year sentence for culpable homicide -- the equivalent of manslaughter.
"Guilty of murder, with the accused having criminal intent," judge Eric Leach told the court in a dramatic legal reversal.
"The matter is referred back to the trial court to consider an appropriate sentence."
The 29-year-old star Paralympic sprinter shot dead Reeva Steenkamp, a model and law graduate, in the early hours of Valentine's Day two years ago.
"He did not know whether that person constituted any threat," Leach said in a damning rejection of the testimony from Pistorius and the original trial judge's ruling.
"It is inconceivable that a rational person thought he was entitled to fire at this person with a heavy-duty firearm," said Leach, who described Pistorius's testimony as "vacillating and untruthful".
"He must have foreseen that the person behind the door might be injured.
"He ought to have been convicted not of culpable homicide... But of culpable murder."
Awaiting his new sentence, he is likely to remain under house arrest at his uncle's mansion in the capital Pretoria.
His trial attracted worldwide attention as he denied killing Steenkamp in a rage after the couple had gone to bed.
"I was overcome with fear," he said while in the dock, describing how he thought he heard an intruder in the bathroom.
He grabbed his gun, and rushed without his prostheses to the bathroom.
(REOPENS FGN 24)
Last month he made his first appearance in public since leaving jail when he reported for community service at a police station in Pretoria.
A Pistorius family spokesman said no statement would be released after Thursday's verdict.
Steenkamp's mother June was in court, but made no immediate comment.
His parole conditions have not been made public, but are reported to require him to meet with Steenkamp's parents if they wish.
Pistorius may make his own appeal to South Africa's Constitutional Court -- the country's highest court.
In the aftermath of the killing, the Paralympic gold medallist lost his glittering sports career, lucrative contracts and status as a global role model for the disabled.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
