The Delhi–Chennai line is a railway line connecting Chennai and Delhi cutting across southern part of the Eastern Coastal Plains of India, the Eastern Ghats, the Deccan Plateau and the Yamuna valley. It covers a distance of 2,182 kilometres (1,356 mi) across Delhi, Haryana, Uttar Pradesh, Rajasthan, Madhya Pradesh, Maharashtra, Telangana, Andhra Pradesh and Tamil Nadu. The route is used by the Grand Trunk Express and as such is referred to by many as the Grand Trunk Route.

The 2,182 km (1,356 mi) long trunk line, amongst the long and busy trunk lines connecting the metros, has been treated in more detail in smaller sections:

The Agra-Delhi chord was opened in 1904. Some parts of it were relaid during the construction of New Delhi (inaugurated in 1927-28).

The Agra-Gwalior line was opened by the Maharaja of Gwalior in 1881 and it became the Scindia State Railway.

The Indian Midland Railway built the Gwalior-Jhansi line and the Jhansi-Bhopal line in 1889.

The Bhopal-Itarsi line was opened by the Begum of Bhopal in 1884. Itarsi was linked with Nagpur between 1923 and 1924.

The period of construction of the Nagpur-Balharshah line is uncertain.

The Vijayawada-Chennai line was constructed in 1899.

The Wadi-Secunderabad line was built in 1874 with financing by the Nizam of Hyderabad. It later became part of Nizam's Guaranteed State Railway. In 1889, the main line of the Nizam’s Guaranteed State Railway was extended to Vijayawada, then known as Bezwada.

With the completion of the Kazipet-Balharshah link in 1929, Chennai was directly linked to Delhi.

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