Irene Mergelsberg was born in Russelsheim in Hesse on 4 March 1893. Later she lived in Frankfurt am Main. She lived in a care home in Kronberg im Taunus since the 1970s. As a centenarian, she still smoked three cigarettes a day. She was a hobbyist painter.
Mergelsberg passed away in Hesse on 6 March 2003 aged 110 years, 2 days. At the time of her death, she was the fifth-oldest person in Germany behind Anna Stephan, Lina Zimmer, Clothilde Rey and Johanne Wilks . She was validated by the Gerontology Research Group on 12 March 2005.