National defense or national defence is the term given to any activity or effort performed to protect a nation against attack or other threats.

Ostensibly, the term should be equivalent to literal military defense, but it may also be applied to offensive actions or policies, or to non-military actions or policies.

For the United States, "National defense" is the name of an area of "tax outlay" (a division of how tax income is spent; other outlays include "Medicare", "Social Security", and "Non-defense discretionary spending").

See also

• national security

Défense nationale