St Johnston, officially Saint Johnstown[3] (Irish: Baile Suingean[3]), is a village, townland, and an electoral division in County Donegal, Ireland.

[6] St Johnston Presbyterian Church, located on the Derry Road, is the other main structure within the village.

The building, however, which serves the large Ulster Scots Presbyterian community in this part of The Laggan, had been fully restored by around 1990.

In the very early seventeenth century, Mongevlin was the chief residence of Iníon Dubh (d. 1608), the daughter of both Séamus Mac Dhòmhnaill, 6th Laird of Dunnyveg, an Islay-based Gaelic nobleman, and his wife, Lady Agnes Campbell; Iníon Dubh was the mother of Red Hugh O'Donnell.

On 23 July 1610, at the start of the Plantation of Ulster, Mongevlin Castle and its lands were granted to the 2nd Duke of Lennox (1574–1624), a senior-ranking Scottish nobleman.

After her husband Esmé's death in August 1624, Katherine, now Dowager Duchess of Lennox, then married the 2nd Earl of Abercorn (c. 1604 – c. 1670), another Scottish nobleman, c. 1632.

[citation needed] A borough was established at the site in the reign of King James VI & I during the early years of the Plantation of Ulster.

[8] St Johnston was one of several Protestant villages in East Donegal that would have been transferred to Northern Ireland had the recommendations of the Irish Boundary Commission been enacted in 1925.