Captain Joshua Allen, 5th Viscount Allen (26 April 1728 – 1 February 1816) was an Irish peer.
The son of Hon. Richard A. Allen, and grandson of John Allen, 1st Viscount Allen, he succeeded to the title of 5th Viscount Allen, County Kildare, and its subsidiary titles, on 10 November 1753, on the death of his brother the 4th Viscount who had died without issue.
He gained the rank of captain in 1758 in the service of the 37th Regiment, under Prince Ferdinand of Brunswick, and fought in the Battle of Minden in 1759.
He was a Member of Parliament (MP) for Eye from 1762 to 1770.
He married Frances Barry, on 5 August 1781. They had two children.