The first constitution to introduce a presidential system was the

To answer the question about which constitution first introduced a presidential system, it is important to understand that a presidential system is a form of government where the president is the head of state as well as the head of government, and there is a distinct separation between the executive and legislative branches.

The constitution that introduced the presidential system for the first time in Nigeria was the 1979 Constitution. This constitution marked a significant departure from the previously used parliamentary system, adopting a system more similar to that of the United States. In the 1979 Constitution of Nigeria, the president was given executive powers, separating this role from the legislature, which was a distinct shift in governance structure. This move aimed to enhance checks and balances, and prevent the concentration of power in a single branch of government.

In conclusion, the 1979 Constitution was pivotal in introducing the presidential system to Nigeria.