Viscount Gormanston is a title in the Peerage of Ireland created in 1478 and held by the head of the Preston family, which hailed from Lancashire.

His son and heir, the second Baron, played a prominent part in public affairs, and was arrested for treason in 1418.

A later descendant, the seventh Viscount, was a supporter of King James II and was outlawed after the Glorious Revolution.

In 1868 he was created Baron Gormanston, in County Meath, in the Peerage of the United Kingdom, which gave the Viscounts an automatic seat in the House of Lords.

His daughter Jane married the 3rd Baron Gormanston, and was the mother of Sir Robert Preston, who was created a viscount.