St Gallgo's Church, Llanallgo (; 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.

The church is associated with the 1859 wreck of the Royal Charter off Anglesey; it was used as a temporary mortuary, and 140 of the victims are buried in the churchyard. Charles Dickens, who wrote about the loss of the ship, noted the care taken by the rector, Stephen Roose Hughes, for the victims and their families. Hughes died a few years later following the strain of the events and is also buried in the churchyard.