Johan de Witt (24 September 1625 – 20 August 1672) was a Dutch statesman and mathematician who was a major political figure during the First Stadtholderless Period, when flourishing global trade in a period of rapid European colonial expansion made the Dutch a leading trading and seafaring power in Europe, commonly referred to as the Dutch Golden Age. De Witt was elected Grand Pensionary of Holland, and together with his uncle Cornelis de Graeff, he controlled the Dutch political system from around 1650 until the Rampjaar (Disaster Year) of 1672. This progressive cooperation between the two statesmen, and the consequent support of Amsterdam under the rule of De Graeff, was an important political axis that organized the political system within the republic.
As a leading republican of the Dutch States Party, De Witt opposed the House of Orange-Nassau and the Orangists and preferred a shift of power from the central government to the regenten. However, the Dutch Republic suffered numerous early defeats in the Rampjaar, due to an alliance of England, France, and several German states which planned on invading the Dutch Republic.