A letter written in April 1917 by Michael Collins to Thomas Ashe reached more than five times the expected price at a Whyte's art sale in the RDS, Dublin last night.
The letter to Ashe, the 1916 Rising leader who later died on hunger strike, was expected to fetch about €50,000 but was eventually sold for €260,000.
Ian Whyte, of Whyte's art auctioneers, said the price was far beyond expectations. He said the letter was bought by a private collector in the south of Ireland.
The letter contains Collins' views of political affairs at the time and makes caustic comments about Arthur Griffith and Éamon de Valera.
There was intense bidding between the anonymous collector and an institution which also asked to remain anonymous.
The letter was sold by the family of Thomas Ashe. The family also sold a portrait of Ashe by the painter Leo Whelan. The painting had been in the family since 1917. The portrait was bought by another Irish bidder for €40,000.
Drawings by Countess Markievicz fetched €15,000 while a 1922 first edition of James Joyce's Ulyssesmade €23,000.
Medals awarded to Irish Volunteer Daniel Tynan were also up for auction. The sale, which was continuing last night, was expected to raise €2 million.