Tonduff is a mountain peak located in the far northeastern section of the Wicklow Mountains in County Wicklow, Ireland. It reaches an elevation of 642 metres (2,106 ft), ranking it as the 169th–highest peak in Ireland on the Arderin scale and the 202nd–highest peak on the Vandeleur-Lynam scale.
The mountain features a main flat summit, which is occasionally identified as Tonduff North. It also possesses a subsidiary summit known as Tonduff East Top (593 metres or 1,946 ft), sometimes referred to as Tonduff South; this secondary peak has a prominence of only 15 metres (49 ft). The surrounding landscape includes the Liffey Head Bog on the western slopes, which serves as the source of the River Liffey, and bogs on the southern slopes that form the source of the River Dargle.