The Greek god associated with the harvest and fertility is Demeter. As the goddess of agriculture, she governs the growth of crops and the process of reaping. Demeter's significance is underscored in the myth of her daughter Persephone, whose annual descent into the Underworld results in the change of seasons. This association encapsulates the cycle of sowing and reaping, teaching the importance of balance, nourishment, and respect for the earth’s resources.