John O’Hanlon’s long-standing record of nine Irish championship wins has been equalled by Stephen Brady, but O’Hanlon still holds one record: he competed in 29 championships.
Even here his record is in some danger, with many currently active players nipping at his heels. The next highest numbers are: Eamon Keogh (28), Colm Daly (27), Anthony Fox and Philip Short (25), Gerard O’Connell (24), and Stephen Brady (23).
I haven’t fully checked other records, such as longest span between first and last championships or most consecutive championships played. For the first, I think Eamon Keogh holds the record (54 years: 1962 to 2016), followed by J. A. “Porterfield” Rynd (48 years: 1865 to 1913) and O’Hanlon (43 years: 1913 to 1956). The second is complicated by the fact that in many early years no championship was held; if we limit it to number of consecutive years in which a player competed in an Irish championship, then O’Hanlon has 13 (1928 to 1940), equalled by John B. Reid, Irish champion in 1961 and 1962 (1951 to 1963), both exceeded by Anthony Fox’s 17 (1995 to 2011).
The list is based on the Irish Championships page at David McAlister’s Irish Chess History website, which contains player lists for almost all championships, making it possible to run scripts to extract number of championships played.