Fionnula O'Brien was a human woman who lived in the 24th century.

She was born in Killarney, Ireland on Earth. As an adult, she married Michael O'Brien, and they had three sons, including Miles. Fionnula and Michael were active foster parents, and took in many children, including Jean Brennan.

Fionnula died in 2368, after a long illness. (DS9: "Whispers")