The Srisailam Water Tunnel-1 is 43.5km long as it crosses the Amrabad plateau which contains a wildlife sanctuary and the Rajiv Gandhi Tiger Reserve. This scheme has been planned since 1983 to provide irrigation facilities to the drought ridden areas of Nalgonda district for 300,000 acres and to supply drinking water to the fluoride affected villages, en-route. The proposal by Jaiprakash Associates to execute the tunnel with a tunnel boring machine (TBM) instead of the Drill and Blast method won favour with the client as it would not disturb the wildlife. The tunnel has an internal diameter of 9.2m and is lined with 300mm thick bolted precast concrete segments. The tunnel traverses through quartzite and granite. This is the world’s longest TBM driven tunnel without intermediate access. The first of the TBMs was launched in March 2008 from the outlet portal site and the second machine from the inlet portal site is due to be launched in November 2009. They are both double-shield rock TBMs. The entire project is expected to be operational by December 2012. This paper describes the design and construction of Tunnel-1.