Trewen (Cornish: Trewynn) is a hamlet and a civil parish in east Cornwall, England, United Kingdom The parish is just east of Bodmin Moor in the River Inny valley and lies in the Registration District of Launceston.

[2] The hamlet of Trewen is situated 5 miles (8 km) west of Launceston.

The parish church of St Michael is in the village at OS Grid Ref SX251835.

"The church is an ancient granite building in the Early Perpendicular style, which was restored in 1863/1864; it comprises a chancel, nave, and north aisle".

[3] The only other hamlet in the parish of Trewen is Piper's Pool which straddles the A395 road.