Great Sugar Loaf, Mountain peak in County Wicklow, Ireland.

Great Sugar Loaf is a mountain in County Wicklow with a distinctive conical shape formed by quartzite rock that sets it apart from the surrounding Wicklow Mountains. The summit reaches about 501 meters above sea level and rises noticeably above the surrounding hills.

The Irish name Ó Cualann means 'lump of Cualu', as recorded by Paul Tempan; a 1935 article by Eoin MacNeill in the Journal of the Royal Society of Antiquaries of Ireland suggested it could mean 'sheep of Cualu' but considered this unlikely. The English name follows the conical sugarloaf shape, a term applied to such hills across Britain and Ireland.

The name "sugarloaf" refers to the conical form in which sugar was sold until the 19th century, before granulated sugar existed; Paul Tempan notes it is often wrongly thought to mean a loaf of bread. The Irish name Ó Cualann means "lump of Cualu".

The shortest route starts at a large car park on the L1031 (Red Lane) along the southern boundary, already at about 290 metres, leaving 210 metres of climbing. The 3.5 km round trip takes 1 to 1.5 hours over flat moorland paths, with a final scramble through rocky gullies. A longer 5 km route from the Kilmacanogue GAA car park takes 2 to 2.5 hours over moorland, scree and gravel.

The two small shoulders on the northern and southern flanks are often mistaken for the Little Sugar Loaf, but that separate mountain lies east across the N11 at Kilmacanogue. The summit's isolation gives it a prominence of 216 metres, enough to qualify it as a Marilyn.