While passenger trains are operated by private operators, motive power is generally provided by the Islamic Republic of Iran Railways (RAI).
Additionally, Alborz Niroo Equipment & Railway Fleet Company runs freight train using privately owned diesel locomotives.
[1] This is an incomplete list of diesel locomotives used in Iran.
(Qty) (137) (14) (2) (20) (183) (80) (10) (21) (34) (7) (69) Steam locomotives have been phased out by Iran Railways.
Sources: from World's Main locomotives and railfaneurope[17] and traction dep.