As of June 2023, which of the following is the longest train route in India?

The train route from Dibrugarh (Assam) to Kanyakumari (Tamil Nadu) operated by the Vivek Express is the longest train route in India. It covers a distance of approximately $4,189\text{km}$ and passes through nine states, making it the longest route in terms of both distance and time in the Indian Railways network.