Cerro Ñemby, Volcanic hill in Ñemby, Paraguay.

Cerro Ñemby is a volcanic hill in the Caaguazú neighbourhood of Ñemby, about 1,450 metres from the city centre. It has the form of a truncated cone with a base diameter of nearly 700 metres. Its solidified basaltic lava, about 45 million years old, was quarried for paving material, and the west side now stands at 154 metres while the east side reaches 206 metres.

The first written references to the hill date from the 18th century, when it was called cerro de La Frontera or Ñemby. Félix de Azara noted it on 8 February 1784, and on 2 September 1784 the pilot Pablo Zizur marked the "cerrito de La Frontera o Ñemby". Aguirre passed through in 1794 and recorded the same name. Old maps also label it Reducto (Mouchez, 1861) and Caaguazú (Gásperi, around 1920).

The name Ñemby may come from a Cario chief who held authority in the area when the conquistadors arrived, or from a Guaraní phrase meaning "stone that came out from inside", referring to the hill's volcanic origin. In old maps it also appears as Reducto, linked to the Jesuits of San Lorenzo, and as Caaguazú, from the Guaraní for "high forest".

The hill lies in the Caaguazú neighbourhood of Ñemby, about 1,450 m from the city centre and roughly 17 km south of Asunción. The west side has been lowered by quarrying to 154 m, while the east side remains the highest point at 206 m. The slopes are rocky with little soil, so wear firm shoes.

The hill's basalt, cooled from lava about 45 million years ago, was quarried for paving material; the 1963 measurement of 206 metres dates from the start of that extraction. The western side, lowered by quarrying, measured 154 metres in a 2019 GPS survey, while the eastern summit still reaches 206 metres.