Joseph Leeson, 4th Earl of Milltown KP (11 February 1799 – 31 January 1866) was an Anglo-Irish peer, styled Viscount Russborough from 1801 to 1807.
In 1811 his mother remarried Valentine Lawless, 2nd Baron Cloncurry, and had three further children, including Edward Lawless, 3rd Baron Cloncurry.
He became Earl of Milltown in 1807 on the death of his grandfather, Brice Leeson, 3rd Earl of Milltown, and was appointed a Knight of the Order of St Patrick on 13 March 1841.
[1] He married Barbara Meredyth, daughter of Sir Joshua Colles Meredyth, 8th Baronet and Maria Nugent, and widow of Eyre Coote, 3rd Baron Castle Coote.
The title is now dormant, as there is still a possible claim through a younger son of the 1st Earl.