Stronsay is 3,275 hectares (13 square miles) in area, and 44 metres (144 feet) in altitude at its highest point.

Sights on the island include the Vat of Kirbister, a natural arch described as the "finest in Orkney",[1] white sand beaches in the three bays, and various seabirds amongst which are Arctic terns.

The coast around Odiness Bay features numerous dramatic geos, caves, flagstone rock platforms and sea stacks, including Tam's Castle, reputed to have once housed a hermitage on its flat summit.

While the landscape has few trees, the fertile soil supports a wide variety of wildflowers, including oysterplant, frog orchids, adder's tongue, and also a naturalised population of Patagonian ragwort.

[1] Both the Rothiesholm Peninsula and coastline of south-eastern Stronsay have been designated Important Bird Areas (IBAs) by BirdLife International because they support breeding seabirds.

[8][9] Two flint arrowheads discovered at a site investigated by Orkney College in April 2007 are believed to date from the late Paleolithic or early Mesolithic periods some 10–12,000 years ago.

A prominent feature of the smaller island is the monastery complex of the Transalpine Redemptorist monks who live there.