Nkosimphile Nkambule died but managed to save her child after the horror attack on August 18 last year.
The Middelburg High Court heard how Morgan Mashiya (30) bought petrol and poured it inside the residence he was sharing with his girlfriend, Nkosimphile, and their daughter.
He then locked them inside their house and pushed a couch in front of the door, to prevent them from escaping before setting the house alight.
The court heard testimony of how Mashiya shouted for help when the house was already engulfed in flames. He managed to throw the house keys outside through a window and escaped the flames.
Nkosimphile managed to cover her daughter with a blanket and also escape the house. She however sustained serious burn wounds and passed away in hospital three days later.
Mashiya was charged with murder, attempted murder and arson. He was sentenced to life imprisonment on the charge of murder as well as five years for attempted murder and five years for arson.
The court ordered the sentences to run concurrently.
The Provincial Commissioner of Mpumalanga, Lieutenant General Semakaleng Daphney Manamela, congratulated the investigating team, prosecutors and the judiciary for their part in the success. She said she believes the sentence will help bring closure to the affected families.