| Mashrak–Thawe Extension Railway | |
| Foundation: | 12 January 1931 |
| Defunct: | 1 January 1943. |
| Predecessor: | none |
| Successor: | Oudh and Tirhut Railway |
| Location Country: | India |
| Area Served: | Northern India |
| Services: | Rail transport |
Mashrak–Thawe Extension Railway was owned by the Government of India and worked by Bengal and North Western Railway.
The 39adj=midNaNadj=mid metre gauge line from Mashrak to Thawe was opened 12 January 1931. The Mashrak-Thawe Extension Railway was merged into the Oudh and Tirhut Railway on 1 January 1943.
The railway line was converted to broad gauge in 2017.