Greek Mythology

Greek Mythology began as an oral tradition, which was later recorded by the likes of Homer in his epic Illiad and the Odyssey. They focus mostly on the Greek Gods, a pantheon of beings who had dominion over various aspects of the Earth and life itself. Some of the more famous Gods are Aphrodite - the Goddess of Love and Zeus - the king of the Gods. They each had their own abilities and were prone to interfering with the affairs of mortals. They were shown to be deeply flawed and guilty of many things such as infidelity and murder. Stories of each God offer lessons which are still relevant today. Aphrodite for example was said to be incredibly vain and jealous and would find ways to punish women believed to be prettier than her. It did not usually end well for the mortals, but sometimes the Gods got their just desserts.
Along with the Gods there were many creatures and monsters in Greek myth such as the Minotaur, a half man, half bull and Medusa - a beautiful woman with snakes for hair, who had the ability to turn men to stone if they looked at her. Some of these creatures were born this way, a byproduct of a God and another monster, or even a human. Or they were cursed to be that way by one of the Gods.
The Gods resided on Mount Olympus and there were 12 original Gods - 

• Zeus
• Aphrodite
• Apollo
• Athena
• Ares
• Artemis
• Demeter
• Dionysus
• Hephaestus
• Hermes
• Poseidon

Hades is usually depicted in many stories too. The brother of Zeus and Poseidon, he has dominion over the Underworld.
The myths and legends featuring the Gods are vast and have shaped literature for thousands of years. Common retellings these days usually feature the Gods Hades and Persephone as they seem to be a popular couple - the Goddess of the Spring and the God of the Underworld. Many readers view this as a love story, rather than focusing on the original version in which Persephone was taken by Hades against her will.
You can find the stories online.