The right of conquest is the purported right of a conqueror to territory taken by force of arms. It is sometimes considered a principle of international law.

Its defenders state that the acknowledgement of this right is simply an acknowledgement of the status quo, and that denial of the right is meaningless unless one is able and willing to use military force to deny it. Furthermore, they note that granting such a right promotes peace, since it removes the justification for many wars by denying the legitimacy of violating the borders of a nation's de facto area of control. Also, historically strength in battle and fitness to command were not considered separate, (see Trial by Combat, and The Divine Right of Kings.)

Some argue that the idea comes from the fact that there have historically been few "good" leaders, (see King Richard I and Pope Alexander VI.) Conquest proved great military strength, and defense was considered one of the most important elements required of a king (see Lord Protector). Someone appealing to the right of conquest was most likely planning on standing as regent, rather than just robbing a land of its riches (like the Vandals and Mongols are regarded as having done).

Its critics respond that it rewards military aggression and thus may serve to promote rather than prevent war.

Modern-day examples where the right of conquest might be appealed to include Israel, Tibet, and mainland China.