SURROUNDED by her family and former students, Sister Madeleine, who is believed to be the world's oldest nun, celebrated her 110th birthday in Young, in southern NSW, on Saturday.

Sister Madeleine devoted 52 years of her life to teaching in the Southern Highlands and she left a mark on her students, some of whom paid her a special visit to mark the occasion.

Staff at the Mt St Joseph's Home in Young, where Sister Madeleine lives these days, described her as "very modest" and a "very lovely lady".

She taught primarily in orphanages and served as an inspiration to the many boys and girls she educated.

Sister Madeleine enjoyed her time teaching very much and continues to hold fond memories of the many children she taught.

One of her former students went on to become a priest with the Canberra-Goulburn diocese. Her former students continue to keep in touch with her and she spends much of her time writing letters to them.

Sister Madeleine didn't have much to say after the celebrations, but she enjoyed the occasion a lot.

She still remains active these days and enjoys reading and listening to Irish singer and performer Daniel O'Donnell. Sister Madeleine is believed to be Australia's second-oldest person.