The Treaty Stone is a rough-hewn limestone block raised on a pedestal standing across the river Shannon from King John's Castle in Limerick City.

Traditionally it is said that it was on this rock that the Treaty of Limerick was signed in the sight of both armies at the Clare end of Thomond Bridge on the 3rd of October 1691.

The treaty marked the surrender of the city to the army of William of Orange. Under the terms, a promise was made to respect Catholicism, but the treaty was rejected by the English and Irish Parliaments and its terms were ignored. Thus Limerick became known as The City of the Broken Treaty.

The stone rests on a pedestal that was erected in May 1865 by John Rickard Tinslay, mayor of the city. The pedestal is decorated with an image of the castle, on the opposite side of the River Shannon, which is surmounted by a dome and cross, signifying that Limerick was a cathedral city. This symbol is now the civic insignia of Limerick Corporation while the Latin inscription is taken from Virgil's description of Troy.