World's longest river cruise sets off on epic 3200-kilometre journey

An India-based luxury cruise vessel has set off on a history-making voyage, chasing the title of the world's longest river cruise.

Antara Cruises's ship MV Ganga Vilas on Friday set sail from Varanasi, known as India's spiritual city, on a journey that will cover a record-breaking 3200 kilometres of river spanning India and Bangladesh.

The historic launch of the 51-day itinerary even garnered a video send-off from the country's prime minister, Narendra Modi, who described the launch as a landmark moment that will "herald a new age of tourism in India."

The 36-passenger, 18-suite ship will operate two sailings per year, between October and March, visiting major cities such as Kolkata and Dhaka, according to Antara's director of sales and marketing Kashif Siddiqui.

The itinerary takes guests through national parks and UNESCO World Heritage listed sites across five Indian states and neighbouring Bangladesh. Its final stop will be at Dibrugarh in India's north.

Scheduled sailings for both 2023-24 have already sold out, and rooms aren't cheap – tickets onboard the luxury vessel range between 4.2 million to 4.5 million rupees ($A74,000 to $A79,000). The bulk of the clientele hail from Switzerland and France, according to the company, who has concentrated its marketing efforts in Europe.

The MV Ganga Vilas, so named for the iconic Ganges waterway it explores, was originally scheduled to launch in 2020, but faced pandemic-related delays.

Antara's first Indian-built vessel stands out with floor-to-ceiling windows, mid century-style design and indigenous furnishings, described on the website as "futuristic". Interior colour schemes featuring magenta and yellow represent the vibrant cultures woven into the itinerary.

Passengers will have access to an onboard sun deck, spa, salon, gym and upmarket restaurant, with cuisine inspired by the ship's various stop-off locations.