Which Indian national highway connects Delhi and Mumbai? The answer is NH 48.
NH 48 is the modern national-highway designation for the major road corridor linking Delhi and Mumbai. That Delhi–Mumbai section runs through Haryana, Rajasthan, Gujarat and Maharashtra, connecting the national capital with India’s financial centre and passing important cities including Gurugram, Jaipur, Udaipur, Ahmedabad, Vadodara and Surat.
The route is longer than just the Delhi–Mumbai connection: NH 48 continues south from Mumbai through Pune and Bengaluru to Chennai, with a total listed length of about 2,807 kilometres. This extended route was created through India’s national-highway renumbering programme in 2010.
A common source of confusion is the older number NH 8. Before renumbering, the Delhi–Mumbai stretch was known as NH 8, while the Mumbai–Chennai stretch was NH 4. NH 44 is now India’s longest national highway overall, but it is not the designated Delhi–Mumbai corridor. NH 48 is therefore the canonical answer for this question.