Bank of Ireland has succeeded in borrowing €1bn on the bond markets, paying interest of 3.125pc for loans over three years.
The "covered bond" deal was the first issued by an Irish bank without a state guarantee for three years.
It will be Bank of Ireland's first public bond of any kind since 2010.
A "covered bond" is a type of IOU that is secured not on the borrower itself but on a pool of assets.
Bank of Ireland is looking to take advantage of the increasingly positive sentiment about Ireland in the markets.
Traders say they have seen strong interest for older Irish bank bonds in recent weeks, which indicates that investors will lend to the banks at much lower rates than would have been expected even last summer.
Reacting to the move, Finance Minister Michael Noonan welcomed the deal.
"The commitment from investors of €1bn in unguaranteed Irish bank paper is important in decoupling the Sovereign from the banks. It is a step towards their full return to wholesale markets, independent of State support," he said.
"The strong investor appetite, as demonstrated by the fact that this issuance was close to 2.5 times oversubscribed, is an expression of confidence in the Irish economy."
Meanwhile, Bank of Ireland is providing €50m of loans to build eight schools under a public private partnership (PPP) deal in the first financing of its kind since 2010.
It is backing the deal in a 50/50 venture with the European Investment Bank (EIB), with support from the National Pensions Reserve Fund.