Was the Lion King based on Christianity?

I would say it has "Christian undertones" or "Christian themes"

Similar to the newly released movie "Raya" -- which talks about division and mistrust taking over and a messianic figure that brings back unity, peace, and saves all the people.

Christianity has had SUCH an impact on Society that its themes exist in MANY forms and movies and even people who claim that they aren't religious or are no longer following any religion -- OFTEN TIMES still live by and hold very Christian ideals and morals. 

To be fair, though -- ideas of 'rebirth' and that life was better in the past and of forgiveness and needing to be 'saved' - are running themes in MANY religions.

Which to the religious only prove that they are TRUE, but to the non-believers is taken as evidence that these ideas are all made up and recycled and nothing about religion is true or unique.

No it was based on Hamlet, the Prince of Denmark.

Narnia series was the religious one with a lion.

No, the Lion King was based on Simba the White Lion, an old Japanese cartoon.

"Disney made Narnia and everyone knows the book has Christian undertones and messages"

Even DISNEY makes stupid mistakes, now and then...

Breakthrough:  "It’s not Christian as far as I know"

Yeah, but you're a Mental Case, so you don't have any credibility anyway.

As for the questioner, you seem crazy enough to find Christianity in a Subway Sandwich

Yes. It's heavily inspired by the story of the prodigal son. You might be surprised on how many Disney movies are heavily influenced by the Bible. Finding Nemo is inspired by the parable of the lost sheep for example. Frozen has strong Christian influences. And the Lion the Witch and the Wardrobe was a deliberate Christian allegory, but I still prefer the BBC version by far. 

Update: Yes, it's true they took it from Kimba the White Lion. But it's also true that the story in the film Disney produced is based on the Bible. The Bible heavily influences so much western literature, it's amazing. Superman is based on Jesus Christ. As a baby he lands in a barn, essentially being born in a barn. He's raised by adopted parents who teach him to be morally perfect. He has special powers to save mankind from itself. His father appears as a ghostly figure who advises Superman who talks to him in solitude. Just like Jesus praying to his father. Actually they changed his mothers name to Martha from the first few comics, where her name was Mary. But that is an example of taking a Biblical figure and creating the story. The superman/Jesus connection was deliberate. 

Also John Carter was Jesus Christ on Mars. 

The Green Mile, John Coffey was based on the Bible. 

It’s not Christian as far as I know but maybe Yoruban 

Someone once said it was based on Shakespeare's play Hamlet, when it came out in cinemas

No.  Disney does not base any the anything on Christianity.  They are a secular company.