The system runs from Rabiya southward through Mosul, Baiji, and Baghdad to Basra, with a branch line from Shouaiba Junction (near Basra) to the ports of Khor Az Zubair and Umm Qasr, westward from Baghdad through Ramadi and Haqlaniya to Al Qaim and Husayba, with a branch line from Al Qaim to Akashat, and east–west from Haqlaniya through Bayji to Kirkuk.

It stretches 550 kilometres to Basra Al Maqal railway station and has a branch line to Karbala and another one from Shoeyba Junction to Um Qasr.

The IRR Eastern Line was the last metre-gauge railway in Iraq connecting Baghdad, Baquba and Kirkuk with Erbil.

Multiple narrow-gauge railways were built in Iraq during the First World War and British Mandate times.

Soon after the end of World War I this was extended northwards from Ur Junction outside Nasiriyah up the Euphrates valley with the complete Basra to Baghdad route being opened on 16 January 1920.

[4] The other section of metre gauge line built during World War I that had ongoing significance was that from Baghdad East north eastwards to the Persian border.

A joint road and rail bridge was opened across the River Tigris in Baghdad in 1950, finally connecting the east and west bank metre gauge systems.

[3] In 1961 IRR began to replace its standard gauge steam locomotive fleet with diesels from ČKD[19][20][21] and Alco.

[3][26] In 1964 IRR extended its standard gauge network with a line from Baghdad to Basrah which opened for freight in 1964 and for passengers in 1968.

[3] From 1980 until 2003 IRR suffered approximately one billion United States dollars' worth of war and looting damage.

In October 2011 the English version of Al-Arabiya News reported that a link between Syria and Iraq near the city of Al-Bukamal would begin operations in 2012.

In August 2011, the Jordanian government approved the construction of the railway from Aqaba to the Iraqi border (near Trebil).

[35] In 2011, a 650 km (400 mi) 250 km/h (155 mph) line between Baghdad and Basra was planned, with the Iraqi Railways and Alstom designing the route.