RSA Insurance said it has agreed to buy online insurance broker 123 Money for €65 million.
The deal, which is subject to regulatory approval, will make RSA Insurance the second largest general insurer in Ireland.
123 Money trades as 123.ie and sells personal insurance products, including motor, home, pet and travel products. It has a current consumer base of about 170,000 policyholders. In the year to the end of March 2010, it generated premium income of €60 million.
The broker has gross assets of around €20 million. It will continue to operate under its own brand and structure.
RSA Insurance chief executive Philip Smith described the acquisition as a "very positive development".