Born Free (1966)

Married couple George Adamson and Joy Adamson have long lived in northern Kenya for George's work as the senior game warden of the region. One of George's primary responsibilities is to deal with dangerous animals that may be chronically threatening to humans, livestock and/or crops. It is in this vein that George and his staff end up killing a man eating lion and its lioness, resulting in their three young female cubs being orphaned. Although difficult to begin, George and Joy are able to wean and take care of the three cubs, who they adopt as pets. But soon, they know they have to provide a more suitable environment for the cubs, namely sending them to Rotterdam Zoo... that is except for the smallest, who they have named Elsa and to who Joy in particular has become attached as the emotional fighter among the three. As Elsa grows into lioness maturity, George and Joy provide her with greater freedom away from their property, which may get her into trouble as a largely tame animal. Ultimately, John Kendall, George's boss, directs them to send Elsa to a zoo like they did with her sisters, especially as with anyone in George's job he is soon being reassigned. Joy cannot bear the thought of Elsa being locked up for the rest of her life, believing that they can reintegrate her back into the wild instead, something that had never been done with a tame lion. John gives them three months to accomplish this task, which most specifically involves getting Elsa to be able to kill for food, other creatures which up to this point she has seen only as fellow playthings, and to be accepted by other lions, most specifically mate with and provide food for a male partner while standing up successfully to female competitors

From IMDB:

Fascinating study of lioness born free...

Fascinating study of lioness born free, but domesticated; then being trained to survive again in the wild. This is a unique film in that it deals with some real issues about making a wild animal a pet and the effect on it because of that. The movie begins with an African game warden, played by Bill Travers, killing an adult lion that is attacking humans but leaves behind three pups. The game warden and his wife, played by Virginia McKenna, decide to take in the pups since they lost their parents and would eventually starve to death in the wild. They are finally able to get them to feed off of their homemade formula and grow, but when it comes time to release them back to the wild the wife's attachment to the smallest that she named Elsa, has grown and they decide to keep her. Elsa quickly becomes their pet and attaches herself to them, but they know eventually she'll have to leave.

They avoid the issue of sending her to a zoo because they want Elsa to be free, but then they must take on the challenge of re-training her for the wild. This turns out to be harder than they expected and their trials with this becomes the subject of the rest of the movie. This is all very well done and helps us realize the difference between pets and animals living in the wild and shows us the respect we should have of the differences.

There is a good balance of sentimentality with reality as this couple thinks hard about every decision it makes thinking not just for themselves but for Elsa. This a unique movie that can be enjoyed by persons of all ages and also teaches us some things that we rarely see on film.

https://www3.zoechip.com/movie/born-free-10004