While rationalism has existed throughout the history of philosophy, it is usually associated specifically with three philosophers during the Renaissance. Who were they?

I would say these three philosophers associated with Rationalism were Rene Descartes, Gottfried Wilhelm Leibniz, and Baruch Spinoza.

They all lived in the 16th century when Rationalism was again at the forefront. Rationalism suggests that we should always use reason and logic in our everyday life, and not focus too much on emotions which may cloud our judgment.