Gravity is a fundamental force of the universe, so it was not "invented" by anyone.

The effects of gravity have been observed since prehistory. However a scientific understanding of gravity did not really begin until the Renaissance.

Leonardo da Vinci was the first to observe that gravity has a rate of acceleration.

Isaac Newton was the first to develop a mathematical equation for gravity that accurately measured the force of gravity both on Earth and between the Sun, Moon and other planets.

Also see What is gravity.