PKP Class ST40 is a new class of cargo diesel-electric locomotives used by the PKP LHS broad-gauge division and various Polish private operators, designated 311D (standard gauge) or 311Da (broad gauge) by its manufacturer, Newag.

The class is a heavily reconstructed Soviet M62 (PKP ST44), using only the underframe.

The body has external walkways instead of an internal passage connecting the cabs.

As of January 2009, there were 20 class 311D completed (15 for PCC Rail and five for the Baltic Railways) and six 311Da for PKP LHS, where they are designated ST40.

The drive unit has been completely changed by installing a more efficient engine by the General Electric company which is placed in one place together with the main generator, compressor and fan.