Smyth was born in Tinny Park, Wicklow, County Wicklow, the son of James Smyth, a Member of Parliament of Ireland for the borough of Antrim, and Mary Agar.
On 5 August 1776, Smyth was created a baronet, of Tinny Park in the Baronetage of Ireland.
[1] In 1779 he was elected to the Irish House of Commons as the MP for Mullingar, serving until 1783.
[2] Skeffington Smyth married Margaret Daly and they had a daughter Maria Elizabeth Smyth who married James Daly, 1st Baron Dunsandle and Clanconal, who was also MP for Galway Borough.
Smyth died aged 52 in County Meath on 9 September 1797.