| Castallack Round | |
| Map Type: | Cornwall |
| Location: | Near Castallack, Cornwall |
| Coordinates: | 50.0739°N -5.5686°W |
| Gbgridref: | SW 448 254 |
| Designation1: | Scheduled monument |
| Designation1 Number: | 1004654 |
| Designation1 Date: | 29 September 1972 |
Castallack Round or Roundago is a prehistoric site near Castallack in Cornwall, England. It is a scheduled monument.
A "round" is a small circular embanked enclosure, with one entrance; they are common in Cornwall, and they date from the late Iron Age to the early post-Roman period.
The site is near the summit of a ridge overlooking the Lamorna valley. Part of the rampart survives; it is composed of large stones and slabs, height about and width, forming an oval enclosure. There was originally a surrounding ditch. On the tithe map of 1840, the round is depicted as having a colonnade of stones leading from the entrance in the south to an inner circular enclosure; John Thomas Blight, describing it in 1865, found that these features had mostly disappeared.
To the north-west of the round there are thick stone walls, height up to : the remains of a structure with an internal diameter of about . This is interpreted as a courtyard house, a type of building that developed in west Cornwall from the 2nd to 4th centuries AD.