Reardon will succeed Mike Krefta, who announced in August that he will be resigning in 2021.
Previously, Reardon has served a tenure at ACE in a variety of actuarial and underwriting roles, before being appointed chief underwriting officer for International Property at ACE Tempest Re in 2005.
Most recently she joined Hamilton Re in 2013 as chief underwriter, and was appointed CEO in 2014, a post she held until 2020.
Her new role will see her sit on the group executive committee and lead Hiscox’s Reinsurance and ILS teams which operate from Bermuda and London.
Bronek Masojada, Hiscox Group CEO, said: “Kathleen brings the market knowledge and leadership skills we need to ensure that Hiscox Re & ILS can take advantage of a hardening market and deliver good returns to our reinsurance partners, ILS investors, and shareholders.
“She will also ensure our offering to cedents evolves as the market evolves. I look forward to working with her and benefiting from her fresh perspective.”
He added: “I would also like to thank Mike Krefta, our current CEO of Hiscox Re & ILs, through his underwriting expertise, energy and commitment, Mike has made an impressive contribution to Hiscox, he leaves with our very best wishes for the next chapter.”