The O'Brien class of destroyers was a class of six ships designed by and built for the United States Navy shortly before the United States entered World War I. The O'Brien class was the third of five classes of destroyers that were known as the "thousand tonners", because they were the first U.S. destroyers over 1,000 long tons (1,016 t) displacement.

Four destroyers in the United States Navy comprised the Cassin class. All served as convoy escorts during World War I. The Cassins were the first of five "second-generation" 1000-ton four-stack destroyer classes that were front-line ships of the Navy until the 1930s. They were known as "thousand tonners" for their normal displacement, while the previous classes were nicknamed "flivvers" for their small size, after the Model T Ford.