The Bank Charter Act 1844, extended to Ireland via the Bankers (Ireland) Act 1845, established a highly restrictive monetary regime in Britain and Ireland, in which currency circulation was to be determined by a mechanistic rule-based approach rather than by bank discretion. This paper analyses the functioning of the Irish banking system during the Great Irish Famine (1845-1850) in the context of this rigid monetary regime, focusing in particular on the role of the government chartered bank, Bank of Ireland. The analysis is based on archival material from the Bank of Ireland Court of Directors, as well as quantitative data detailing note issue by Irish banks. This paper contends that while Bank of Ireland was focal point of the Irish banking system during the famine years, it perceived itself at this time primarily as a commercial bank operating within the prevailing monetary regime rather than as a central bank-type entity. Indeed, subsequent characterizations of Bank of Ireland as a “de facto” Irish central bank during the 1840s run the risk of overestimating the level of institutional agency possessed by Bank of Ireland within the wider monetary regime during the famine years