This course shows how to mathematically prove the well-known Kepler's laws. The mathematical equations are derived and solved step-by-step. First, the two-body problem is formulated by using Newton's laws of motion and the universal law of gravitation. Then, the equations are solved, still preserving the physical intuition behind them. Besides, the conservation of the angular momentum, energy of the planet will be motivated and important parameters of the orbit such as: perihelion, aphelion, period, are explicitly written in terms of the energy, angular momentum, mass of the planet, etc., in order to show how the former are affected by the latter.