The British Rail Class 311 alternating current (AC) electric multiple units (EMU) were built by Cravens at Sheffield in 1967. They were intended for use on the line from Glasgow Central to Gourock and Wemyss Bay, which was electrified in 1967.

Outwardly, the units were virtually identical to the earlier Class 303 units built in 1960. The interiors were also very similar, including the panoramic full forward passenger view through the glass-walled driving cabs, although the Class 311 had fluorescent lighting instead of the tungsten filament bulbs used on the Class 303. The Class 303 units had been built by Pressed Steel at their factory in Linwood, Paisley, but by the time the Class 311 was required, Pressed Steel no longer built railway carriages, so Cravens of Sheffield worked to the same original drawings, updated at a few points, to build the new trains.

After being withdrawn from normal traffic, two units, 311103/104 were transferred to departmental duties as Class 936 Sandite units, numbered 936103/104. These lasted in service until 1999, when they were withdrawn. In 2002, Railtrack donated one of the units to the Summerlee Heritage Park Museum in Coatbridge, and the other was scrapped in 2003. One of the driving coaches on the unit donated to Summerlee was scrapped in 2006.