Groma Rock (, ) is the 45 m long in south-north direction and 30 m wide rock off the northwest extremity of Low Island in the South Shetland Islands. Its surface area is 0.1 ha.
The feature is named after the ancient Roman surveying instrument groma, and in association with other names in the area deriving from the early development or use of geodetic instruments and methods.
Groma Rock lies in Osmar Strait at , which is 370 m north-northwest of Dioptra Island and 1.75 km north-northeast of Cape Wallace. British mapping in 2009.