When Sirga was just a baby lion cub, she was abandoned by her pride.
Sensing an opportunity to save a life, Botswana-based wildlife caretaker Valentin Gruener took it upon himself to care for her.
Sirga is now full-grown, weighing in at an incredible 310 pounds. Watch the footage above to see the longtime best friends at play and on the prowl.
A new documentary series "Lionheart" will capture Gruener teaching Sirga to hunt, so one day she can live out in the wild.
The series is set to be released worldwide in 2015.