The D-Type, commonly known as the Triplex, was a New York City Subway car class built by Pressed Steel Car Company. They were operated by the Brooklyn–Manhattan Transit Corporation (BMT) and its successors, which included the New York City Board of Transportation and the New York City Transit Authority (NYCTA). The fleet consisted of 121 cars, each arranged as three-section articulated units. Four units were built as a prototype in 1925, and the production units were built during 1927 and 1928.

The D-types were the first articulated rapid transit rolling stock used in the United States, and were followed by several more articulated trains until the BMT sold all of its transit operations to the City on June 1, 1940. First placed into service in 1925, they operated primarily on the BMT's Southern Division, although they would also appear on many other parts of the subway system. The R27s, R30s, and R32s slowly replaced the triplex cars, which last ran on July 23, 1965. Three sets and a section were preserved, and the rest were scrapped.