John Plunkett, 3rd Baron of Dunsany

John Plunkett, 3rd Baron of Dunsany (died 1500) was an Irish nobleman.

He was the only son of Richard Plunkett, 2nd Baron of Dunsany,

In 1487, like the great majority of the Anglo-Irish nobility, he made the mistake of supporting the claims of the pretender Lambert Simnel to the English throne. Simnel was crowned in Dublin, and invaded England with a largely Irish army, but his cause was crushed at the Battle of Stoke. The victorious King Henry VII, the founder of the Tudor dynasty, was magnanimous in victory - Simnel was pardoned, and Dunsany and his fellow peers in 1488 performed an act of public penance for their rebellion and in their turn also received a royal pardon. The King however could not resist playing a joke by inviting all of the Lords Temporal of Ireland, then 15 in number including Dunsany, to a banquet at Greenwich in 1489, where to their embarrassment Simnel, now a servant in the royal kitchen, waited on them at table.

Dunsany attended the Parliament of Ireland in 1490 and 1493. He was fined forty shillings for his non-attendance at the Parliamentary session of 1498 in Castledermot.