Which french king was called the 'Sun King'?

King Louis IV was known to be the sun king by his subjects.

His mother inflated the mind of Louis IV that he was born by the will of God and she also told him that all men are not chosen for kingship. He was driven by the thought that he was the chosen and opted Sun to be his symbol. He is also known to be the Apollo king of France.

He built the magnificent palace of Versailles which was a common stadium turned to royal monument after his death.

Louis XIV

Explanation:

He chose the sun as his emblem.