Oscar Pistorius given six years for Reeva Steenkamp murder
The verdict comes after his initial five-year conviction for manslaughter was changed to murder last December on appeal.
He was taken immediately to jail. Both the prosecution and defence can appeal.
Pistorius, 29, shot Reeva Steenkamp four times through a locked toilet door in February 2013.
He admitted shooting her, but said he mistook Ms Steenkamp for an intruder and acted out of fear.
In an hour-long session, Judge Thokozile Masipa said mitigating circumstances, such as rehabilitation and remorse, outweighed aggravating factors for deviating from the prescribed 15-year sentence for murder.
Dressed in a dark suit, Pistorius listened to the judge mostly with his head down.
Ms Steenkamp's parents, Barry and June, sat on the other side of the courtroom, which was packed with journalists and observers.
Pistorius has already served one year in jail over his previous conviction.
He is legally obliged to serve half of his new sentence in prison before being eligible for parole.
Right after the session, he was transferred to Khosi Mampuru prison in Pretoria.
The six-time Paralympic gold medallist made history by becoming the first amputee sprinter to compete at the Olympics, in 2012 in London, running on prosthetic "blades".
He had his legs amputated below the knee as a baby.
Source: bbc.com