Duff Hill, Mountain summit in County Wicklow, Ireland

Duff Hill is a mountain summit in the Wicklow Mountains reaching about 720 meters in elevation. The peak rises as part of the broader mountain range that shapes the landscape of County Wicklow.

Duff Hill takes its Irish name, An Cnoc Dubh, from the dark colour of its slopes. At 720 metres it ranks 78th on the Arderin scale and 97th on the Vandeleur-Lynam list, and it forms part of the Mullaghcleevaun massif, whose 849-metre summit lies to the south. The neighbouring peak of Gravale, 718 metres, stands immediately to the north.

The Irish name An Cnoc Dubh means "black hill", a description of the peak's dark peaty slopes. The English form Duff Hill comes from the Irish dubh, meaning black, so both names say the same thing in two languages.

Duff Hill sits between Gravale (718 m) to the north and the Mullaghcleevaun massif (849 m) to the south, so it is usually crossed on a ridge walk between the two rather than climbed alone. The ground is open mountain terrain with no marked path or facilities; walkers need map, compass and waterproof boots. Cloud can cover the 720 m top quickly, so check the forecast before setting out.

The peak qualifies as an Arderin, meeting the classification of 30 meters prominence, and is recognized by climbers as a registered summit. This designation makes it a sought-after destination for those completing specific mountain collections.