The Castro of Castelo Velho (Portuguese: Castro de Castelo Velho) is a Chalcolithic settlement in the civil parish of Terena (São Pedro), municipality of Alandroal in the Alentejo Central area of the Portuguese Alentejo.

[1][2] The old castle is situated in an isolated, rural area delimited by the Rio Lucefecit and smaller affluent, overlooking the territory of high hilltops and eastern flanks.

[2] Along the northern flank, is a small, irregular gallery related to the probable mining or possible ritual space.

[1][3] The defensibility of the settlement was secured by its location in an elevated position, protected by the river and its inclined eastern and western margins.

[1][2] Close to this is the principal entrance to the settlement is a schist platform, where there are visible ceramics, foundry slag and remnants of structures that could correspond to an area of marginal habitation related to metallurgical activities.