The U.S. Senate Appropriations Subcommittee on Defense is one of twelve subcommittees of the U.S. Senate Committee on Appropriations. Military defense spending is the largest individual component of federal discretionary spending, making the Defense Subcommittee one of the more powerful Appropriations subcommittees. When referring to federal discretionary spending as a whole, many budget analysts make a distinction between defense and non-defense discretionary spending. The United States Senate Committee on Appropriations has joint jurisdiction with the United States House Committee on Appropriations over all appropriations bills in the United States Congress. Each committee has 12 matching subcommittees, each of which is tasked with working on one of the twelve annual regular appropriations bills.

The United States Senate Committee on Appropriations is a standing committee of the United States Senate. It has jurisdiction over all discretionary spending legislation in the Senate.