Luke Gardiner was born into a wealthy family of urban developers on Dublin's north side. During his lifetime he sat to several eminent artists such as Francis Cotes and, following his election to the Society of Dilettanti in 1773, he also sat to Sir Joshua Reynolds. In the same year Reynolds painted the famous portrait of the three Montgomery sisters, the 'Irish Graces', at Gardiner's request. His most noteworthy property developments were Mountjoy Square and Rutland Square in Dublin.
Gardiner also had political ambitions and entered the House of Commons in 1773. He was raised to the peerage as Baron Mountjoy in 1790 and six years later became a Viscount.