The Ennis Shield is the third division of the Leinster Chess Leagues run by the Leinster Chess Union. Founded in 1926, it was originally the second division of the leinster leagues with it top teams promoted to the Armstrong Cup, in 1971 another league the Heidenfeld Trophy was formed as the 2nd tier of Leinster Chess. The League and trophy is named after Maj. Ennis who presented the trophy to the League. Teams in the League consist of six players, and there are twelve teams in the league. The winning two teams get promoted to the Heidenfeld Trophy and the bottom two teams get relegated to the O'Hanlon Cup.
The first Ennis Shield 1926-1927 season, was competed for by UCD and Irish Army GHQ the lowest two teams in the previous seasons Armstrong Cup, they were joined by teams from Rathmines, The Jewish Union, Dublin Corporation and Non Commissioned Army Officers side.