St Gallgo's Church, Llanallgo (/lænˈælɡɒ/; Welsh: [ɬanˈaɬgɔ]) is a small church near the village of Llanallgo, on the east coast of Anglesey, north Wales. The chancel and transepts, which are the oldest features of the present building, date from the late 15th century, but there has been a church on the site since the 6th or early 7th century, making it one of the oldest Christian sites in Anglesey. Some restoration and enlargement took place during the 19th century.