Constantine V was a king a long long time ago. He lived in a place called Byzantine Empire, which was kind of like a big kingdom ruled by an emperor.
Constantine V was one of the emperors of the Byzantine Empire. He became a king when his dad died and he took over the throne. He was known as a powerful king who was really good at leading his army in wars.
Constantine V believed in a religion called Iconoclasm, which means he didn't like people worshiping religious icons or pictures. He thought it was wrong to make pictures of God or Jesus because it was like making them into things that could be sold or bought.
Some people in the Byzantine Empire didn't like this and wanted to keep making and using icons. So they didn't really like Constantine V.
During his reign, he had to fight against many enemies to protect his kingdom. He also tried to spread his religion by destroying icons and punishing people who used them. Some people didn't like this and there were lots of protests against him.
In the end, Constantine V died, but he left a big mark on history because of his beliefs and actions.