Katherine Plunket was born in County Louth on Nov 22, 1820 and died  on Oct 14, 1932 at the age of 111. She, therefore, became a super-centenarian on reaching the age of 110 in 1930.

Since 1932 Plunket has held the title of Ireland’s oldest living person ever – until now. Syracuse, NY resident Kathleen Hayes Rollins Snavelly, a Clare native, has surpassed her.

Plunket was a member of the Irish aristocracy. She was a granddaughter of a Lord Chancellor of Ireland, who became the first Baron Plunket.

Her father was a junior clergyman when she was born and later became a bishop. He also inherited the title and became the second Baron Plunket. Her mother was the daughter of a Speaker of the Irish House of Commons and was related to the Earl of Clermont. She met Walter Scott the famed novelist.

She was the eldest of six children, though one of these died soon after birth. She also, for a time, had a house in London. She traveled extensively, often with her younger sister Gertrude, and visited almost every capital in Europe. She was an amateur artist and made many sketches in Italy and Switzerland.

Her first and second cousins included three titled members of the Irish aristocracy. She was baptized in Kilsaran Church, on Dec 13, 1820 as Catherine Plunket, though she spelled her name with a "K" for her entire life.

She inherited from her mother one of the family's ancestral homes, Ballymascanlon House near Dundalk, and oversaw the upkeep of the home and gardens until she contracted bronchitis at the age of 102 which was her only serious health problem.The house is now a hotel.

As the daughter of a baron, her full title was the Honourable Katherine Plunket. She had regular entries in the reference books of the period, namely Whittakers Peerage, Burkes Lodges Peerage and Baronetage, and Kelly's Handbook to the Titled, Landed and Official Classes.

She never married and she outlived all her sisters. After her sister Gertrude died in 1924, she lived alone with her servants, but continued to be visited by other members of her family.

When she reached the age of 109 she was sent a telegram of congratulation by King George V. Julia Hynes traced many articles about her in the Irish newspapers on her 103rd, 107th, 108th, 109th, 110th, and 111th birthdays.

When she died, King George V sent a telegram of condolence to her relatives. She had obituary notices in the London newspapers The Times and The Morning Post, and in the Irish newspapers.
She died on Oct 14,1932 at Ballymascanlon House, County Louth.

Her death was registered on Oct 17, 1932 in the district of Ravensdale in the union of Dundalk in Louth. Her name is given as The Hon Katherine Plunket, spinster, aged 111 years and 11 months, occupation Lady. The certified cause of death was syncope.