The NZR RM class 88-seaters were a class of railcar used in New Zealand. New Zealand Government Railways (NZR) classified them as RM (Rail Motor), the notation used for all railcars, numbering the 35 sets from RM100 to RM134. They were the most numerous railcars in NZR service. Their purchase and introduction saw the demise of steam-hauled provincial passenger trains and mixed trains, and was part of a deliberate effort to modernise NZR passenger services at a time of increasing competition from private motor vehicles. Being diesel powered and lighter the railcars were less expensive to operate and able to maintain quicker timetables, although became plagued with mechanical and electrical problems, with a number of the class eventually being turned into depowered locomotive-hauled carriages and reclassified as the AC class "Grassgrubs".

The RM class was the classification used by the New Zealand Railways Department (NZR) and its successors gave to most railcars and railbuses that have operated on New Zealand's national rail network. "RM" stands for Rail Motor which was the common name at the turn of the 20th century for what became known in New Zealand as railcars. As many types of railcars are operated, class names have been given to each railcar type to differentiate them from others.