Tidenham (/ˈtɪdənəm/)[1] is a village and civil parish in the Forest of Dean of west Gloucestershire, England, adjoining the Welsh border.

Offa's Dyke runs through the western part of the parish, terminating at Sedbury cliff above the River Severn.

[4] Tidenham, Beachley and Woolaston were added to Gloucestershire by the first Act of Union of England and Wales in 1536; previously they had been part of the Marcher lordship of Striguil.

Also notable is the former Dayhouse Quarry which, after providing traffic for the remaining fragment of the former railway to Monmouth, is now home to the National Diving and Activity Centre.

The railway, which once ran from Chepstow through Tintern up the Wye Valley, and joined the mainline near Tidenham, was closed in 1959 and was later the centre of several failed attempts to re-open it.