Selene; Goddess of The Moon

Selene is the Greek Titan (one of the immortal Grandchildren of Gaia and Uranus) Goddess of the Moon; or, the personified divine being of the Moon. She is worshipped at the Full and New Moons.

Selene is depicted as a woman riding sidesaddle on a horse, with a crescent moon diadem upon her head. The Greeks believed that at dusk she pulled the Moon across the sky in her chariot pulled by two beautiful white horses. At dawn as Selene waned, her sister Eos arrived with the Sun, which is then pulled across the sky in all its fiery glory by their brother Helios in his chariot of Fire.

She is often identified with other Goddess', such as Artemis or Diana, Goddesses of the Hunt.

The earliest depictions in art of Selene are believed to be around 5th Century BC.

"The Astera (Stars) hide away their shining form around lovely Selene (the Moon) when in all her fullness she shines over all the earth."
- Sappho (c. 6th Century BC)

The Story of Selene and her love, Endymion

One of her most famous depictions (particularly in classical paintings like those above) is alongside her love - the mortal Endymion. Selene asked Zeus to grant him eternal sleep, so that he would not age and die.

"Working as a shepherd, Endymion would often be found tending his flocks at night, and so the beauty of the mortal was observed by Selene in her nightly passage. Taken by the beauty of the shepherd, Selene fell in love, and would long to spend eternity with Endymion. Selene though was immortal, whilst Endymion would age and die.

Zeus (God of the Sky) had no desire to make Endymion immortal in the traditional sense, but instead came up with a solution where the shepherd would not age or die, and enlisting the help of Hypnos (God of Sleep), Endymion was placed into an eternal sleep.

Thereafter, Endymion would sleep in a cave upon Mount Latmos, a cave which Selene would visit every night. Endymion would sleep with his eyes open, so that he too could gaze upon his lover." - Source - greeklegendsandmyths.com

Additional Sources & Reading:
Images from Pinterest and Wikimedia commons. Selene Wax Seal Jewellery Designs are exclusive property of Dixi & Chaser Spaeth and should not be copied and/or redistributed. 
Celestial Goddess Selene (ancient-origins.net)
SELENE - Greek Goddess of the Moon (theoi.com)
Selene (greekmythology.com)
Selene - Greek and Roman mythology (britannica.com)