The term four piper, also known as a1 four stacker, is United States Navy terminology for classes of destroyers with four funnels. These include the classes listed below:
- Cassin-class destroyer
- Bainbridge-class destroyer
- Paulding-class destroyer
- Wickes-class destroyer
- Clemson-class destroyer
These classes were built for use by the United States Navy during World War I and subsequently "moth-balled". Fifty were loaned, under the Destroyers-for-bases deal, to the United Kingdom when convoy escorts were desperately needed in the early years of World War II.