The third USS Decatur (DD-341) was a Clemson-class destroyer in the United States Navy following World War I. She was named for Stephen Decatur.

On September 3, 1939, the British and French declarations of war on Germany initiated the Battle of the Atlantic. The United States Navy Chief of Naval Operations (CNO) established a combined air and ship patrol of the United States Atlantic coast, including the Caribbean, on 4 September, President Franklin D. Roosevelt declared the United States' neutrality on 5 September, and declared the naval patrol a Neutrality Patrol. Roosevelt's initiation of the Neutrality Patrol, which in fact also escorted British ships, as well as orders to U.S. Navy destroyers first to actively report U-boats, then "shoot on sight", meant American neutrality was honored more in the breach than observance.