The world's best-known Paralympian was taken into custody yesterday after Reeva Steenkamp, 30, was shot dead at his exclusive South African home.
He broke down in tears as he appeared in court this morning accused of her premeditated murder at the luxury gated Silver Lakes Golf Estate in Pretoria.
Pistorius, 26, sat with his head bowed when he was brought before magistrates and began to sob, covering his face with his hands, as the charge against him was read out.
Chief magistrate Desmond Nair told him: "Take it easy. Come take a seat."
The gold-medal winner, who earned his Blade Runner nickname because of his prosthetic racing legs, was supported by his father Henke, brother Carl and sister Aimee as prosecutors said they would pursue a charge of premeditated murder.
His family and management company later issued a staunch denial of the allegation on behalf of the track superstar.
They said: "Firstly, and most importantly, all our thoughts today must be with the family and friends of Reeva Steenkamp.
"Oscar Pistorius has appeared in court here in Pretoria this morning formally charged with the murder of Reeva Steenkamp. The alleged murder is disputed in the strongest terms."
The statement added: "Oscar Pistorius has made history as an Olympic and Paralympic sportsman and has been an inspiration to others the world over.
"He has made it very clear that he would like to send his deepest sympathies to the family of Reeva.
"He would also like to express his thanks through us today for all the messages of support he has received - but as stated our thoughts and prayers today should be for Reeva and her family, regardless of the circumstances of this terrible, terrible tragedy."
Pistorius was met by a media frenzy as he arrived at the packed court dressed in a grey suit and blue tie this morning.
Earlier, he attempted to obscure his identity, covering his face with a jacket and a note pad as he was driven into the precincts.
The hearing came after a two-hour delay while the athlete's lawyers objected to the scrum of local and international reporters who turned out to witness his appearance.
During the hearing before magistrates, lawyers representing the athlete asked to postpone an application for bail until next week to "allow time for their own investigation into the circumstances of the tragedy", his management company said.
Pistorius's arrest yesterday triggered shock across the globe and prompted rumours that he might have mistaken his girlfriend for an intruder in what could have been a Valentine's Day surprise gone wrong.
But police swiftly distanced themselves from the suggestion and said there had been previous incidents of a "domestic nature" at Pistorius's property.
Steenkamp's body was discovered at around 3am after neighbours reported hearing screams and gunshots from the sprinter's home.
According to the Beeld newspaper, the model was blasted four times through a bathroom door.
Officers said she was shot in the head and upper body. They recovered a 9mm pistol from the scene.
Since then, there has been heated speculation over what occurred in the early hours of the morning.
A picture has emerged of a volatile man who was said to sleep with a revolver by his bedside and a machine gun by his window amid fears for his safety.
He began dating Steenkamp, a law graduate, in November and the couple were dubbed the Posh and Becks of South Africa.
She had apparently been looking forward to Valentine's Day.
On Wednesday she tweeted: "What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay."
Her publicist Sarit Tomlinson paid tribute to "the sweetest human being and an absolute angel on earth" following her death and said the model was "about to hit the big time".
Asked about Steenkamp's relationship with Pistorius, Ms Tomlinson told BBC Radio 5: "They had been together for a couple of months and it's been a fabulous relationship - a healthy, fabulous relationship."
She spoke out as the athlete was taken to Pretoria's Mamelodi Day Hospital in a police convoy for a "standard" medical examination.
Meanwhile, forensic officers carried out searches at his home.
A gun was later pictured in what appeared to be an evidence bag.
Pistorius made history at the London 2012 Olympics by becoming the first amputee sprinter to compete in the Games, running in the 400m and 4x400m relay.
The star was born without fibulas and underwent below-the-knee amputations at 11 months old.
He had to win a legal battle over his blades with the International Association of Athletics Federations (IAAF) in 2008 for the right to compete in able-bodied competition.
Pistorius's father said his son was "sad" following the shooting.
Mr Pistorius told SABC radio news: "I don't know the facts. If anyone makes a statement, it will have to be Oscar. He's sad at the moment."
South Africa's M-Net cable TV channel pulled adverts featuring the star off air immediately after his arrest.
Sports apparel group Nike, along with most of his sponsors, said they would not make any decisions until the police investigation was completed.
His sponsorship deals - with firms including BT, sunglasses maker Oakley and French designer Thierry Mugler - are thought to be worth as much as £1.3 million a year.
Pistorius will be held at a local police station until his next court appearance, after today's proceedings were adjourned.
A bail hearing is scheduled for next Tuesday and Wednesday, when police are expected to oppose the application.