At a hearing Monday, prosecutors indicted Pistorius in the Valentine's Day shooting death. Pistorius has been charged with planned and premeditated murder, which comes with a mandatory sentence of life behind bars.
The indictment says "the accused did unlawfully and intentionally kill a person."
Pistorius also was indicted for allegedly violating South Africa's firearms control act.
In South Africa, people can possess ammunition only if they're licensed to own a gun, and their ammunition must be specific to that weapon. Pistorius has acknowledged storing ammunition for a gun his father owned.
Steenkamp would have turned 30 on Monday.
The indictment follows the completion of the police investigation into the case.
The double amputee track star killed the woman he calls the love of his life in his home. He denies the murder charge and says he mistook her for a home invader.
The first phase of the trial will take place in March, but the entire trial could take place at various times across a year or more because of potential motions and postponements along the way.
In the indictment, the prosecutors included a list of more than 100 witnesses the state might call. The Pistorius legal team has not released a witness list.
The police investigation team "is convinced that the accused has a charge to answer," a police statement said last week.
A tearful Pistorius
A phalanx of reporters snapped pictures of an emotional Pistorius as he entered the courtroom Monday. While the Olympic sprinter largely maintained his composure, an occasional tear streamed down his cheek.
Before the proceedings started, he held hands with his brother and sister as they appeared to pray.
The athlete's family said in June that he would resume running using his blade-shaped prosthetic legs. Pistorius has started sprinting again for the sake of his emotional health, not for training to compete again, the family said.
Michael Steenkamp, the victim's uncle, said the model's family isn't focusing on Pistorius' guilt or innocence, and they will not attend any of the related court proceedings.
The family said it would be spending time together remembering Steenkamp on Monday.
"My wife and myself are going up to (see) my brother in Port Elizabeth, and we will be there with (Steenkamp's parents) on Monday to be there for Reeva's birthday. What could we do? Bake a cake and, you know, sit down quietly and reminisce about the qualities of Reeva's life," he said.
The uncle said his faith has helped him forgive Pistorius.
"If I can't forgive him, and I have been forgiven, then that is our sin. And I very much asked the Lord to guide me before I got to Port Elizabeth when the tragedy happened ... that took a lot of pressure off my shoulders," he said.
CNN's Kelly Phelps, Joseph Netto and Ed Payne contributed to this report.