Which Federalist paper discusses the separation of powers?

Federalist #51 is the key document that discusses the separation of powers within the government. In this paper, James Madison articulates the necessity of establishing separate branches of government to prevent any one branch from becoming too powerful. He emphasizes the importance of checks and balances, arguing that each branch should have the ability to counteract the others to maintain accountability and limit tyranny. This concept is foundational to the structure of the U.S. Constitution, ensuring that legislative, executive, and judicial powers are distinct and operate independently, yet still interact in ways that uphold democratic principles.

The other Federalist Papers mentioned focus on different aspects of governance. For instance, Federalist #10 addresses the problem of factions and the need for a large republic to mitigate their effects, while Federalist #68 deals with the election of the president and the Electoral College. Federalist #71 relates to the duration of the president's term and the nature of executive power. Hence, Federalist #51 stands out specifically for its discussion on the separation of powers and the mechanisms designed to prevent the concentration of power in any one branch of government.