The NZR EO class of 1923 were electric locomotives used on the steep Otira to Arthurs Pass section of the Midland Line in New Zealand.

They were primarily needed for pulling trains through the 1 in 33 grade 8.5 km (5.3 mi) Otira Tunnel which was too long and steep to allow steam locomotives to be used.

They were later reclassified EO to avoid confusion with the EC class locomotives.

[3] They were referred to as "trams", a term carried over to the 1968 Toshiba replacements.

The locomotive arrived at the Ferrymead Heritage Park in 1972 and was restored to operating order in 1977.