Bertraghboy Bay is a coastal bay on the Connemara coast of County Galway, open to the Atlantic. It is situated near the village of Roundstone, which lies on the bay's western arm. The bay offers a potential sheltered escape point during multi-day expeditions along this coast. For access, the village of Roundstone provides a small boat harbour with quays that can be used at high tide, though the harbour has a bar with a depth of only 0.6 metres extending across it. The harbour is exposed to south-by-southeast winds, but shelter from these can be found by moving into the adjacent Bertraghboy Bay. Mweenish Island, a large island connected to the mainland by a road bridge, is located southeast of the bay's entrance. The passage under the Mweenish bridge is passable for kayaks at the higher parts of the tide. The area is known for its scenic beauty, set against the backdrop of the Twelve Bens mountain range and Errisbeg Hill. The bay is a working area with fishing activity, and it is also a venue for traditional Galway Hooker sailing and rowing races. Paddlers should plan their trips around the significant tidal range common to this Atlantic coast, particularly when navigating the bar at Roundstone or the bridge passage at Mweenish, and be prepared for exposure to prevailing winds and ocean swell.