Lady (Charlotte) Eleanor Butler, elder of the two Ladies of Llangollen, was born at Cambrai, the youngest daughter of Walter Butler of Garryricken and his wife, Eleanor. Her family, whose seat was Kilkenny Castle, considered her an over-educated bookworm. She was educated in a convent in France and so spoke French. Apparently of too ‘satirical’ and ‘masculine’ a cast of mind to make the advantageous marriage that might help restore the Butler family fortunes, Lady Eleanor seemed doomed to a life of narrow solitude when, in 1769, and aged almost thirty, she met Sarah Ponsonby.
On the night of 30 March 1778, disguised as men and armed with pistols, Ponsonby and Butler fled their homes and made for Waterford, Ireland and the boat for England. Their families caught up with them two miles from the port, and they were ignominiously brought back as prisoners. Not daunted, both ladies successfully escaped Ireland shortly thereafter.
Accompanied by Mary Carryll, the devoted Woodstock housemaid, Butler and Ponsonby for a time toured north Wales, finally settling at Plas Newydd, a rented cottage on the outskirts of the village of Llangollen.
Putting their plan into motion, they undertook a picturesque tour of the Welsh countryside, eventually settling in North Wales. Living first in a rented home in the village of Llangollen, they moved in 1780 to a small cottage just outside the village they called Plas Newydd or "new mansion". They proceeded to live according to their self-devised system, though they could rely on only a modest income from intolerant relatives, and eventually a civil list pension. They "improved" Plas Newydd in the Gothic style with Welsh oak panelling, pointed arches, stained glass windows, and an extensive library, in which they received their many guests. They hired a gardener, a footman, and two maids. This led to significant debt, and they had to rely on the generosity of friends.They then began to live the ‘retirement’ that would make them famous. It was a life almost conventual in its simplicity, lived according to a strict timetable, regulated by careful, if not always very accurately kept, accounts, concentrating on good works (though in moderation), self-improvement, reading, gardening, and delicious meals.
They devoted their time to hosting a range of friends and curious visitors, extensive correspondence, private studies of literature and languages, and improving their estate. Over the years they added a circular stone dairy and created a sumptuous garden. Eleanor kept a diary of their activities. Llangollen people simply referred to them as "the ladies".
After a couple of years, their life attracted the interest of the outside world. Their house became a haven for visitors travelling between Dublin and London, including writers such as Anna Seward, Robert Southey, William Wordsworth, Percy Shelley, Lord Byron and Sir Walter Scott, but also the military leader the Duke of Wellington and the industrialist Josiah Wedgwood; aristocratic novelist Lady Caroline Lamb, who was born a Ponsonby, came to visit too. Anne Lister from Yorkshire visited the couple, and was possibly inspired by their relationship to informally marry her own lover. Even travellers from continental Europe had heard of the couple and came to visit them, for instance Prince Hermann von Pückler-Muskau, the German nobleman and landscape designer, wrote admiringly about them.
The ladies were known throughout Britain, but have been said to have led "a rather unexciting life". Queen Charlotte wanted to see their cottage and persuaded King George III to grant them a pension. Eventually their families came to tolerate them.
Butler and Ponsonby lived together for 50 years. Their books and glassware carried both sets of initials and their letters were jointly signed. Towards the end of their lives, they both dressed in black riding habits and men's top hats; some visitors thought it was eccentric and outdated – especially the hair powder – but neighbours thought the clothes were practical for living outdoors.
Rumours that they were in a sexual relationship floated around during and after their lives. In 1791, a magazine described them and implied that they were in a sexual relationship. According to Patricia Hampl, they were appalled by this idea, and objected to the magazine's characterisation to the point of consulting Edmund Burke over the possibility of suing the magazine for libel.
In sharp contrast to the writings of their contemporary Anne Lister, there is nothing in their extensive correspondence or diaries that indicates a sexual relationship. Some consider Butler's and Ponsonby's relationship to be a Boston marriage, or a romantic relationship between two women who chose to live together and have "marriage-like relationships". Others conclude that the two had a non-sexual romantic friendship. Norena Shopland says that modern attitudes designed to distinguish same-sex relationships from a romantic friendship indicate they had a sexual relationship. According to Fiona Brideoake, the description of queer is more appropriate than the anachronistic[how?] and specific label of lesbian, particularly as queerness is a broad concept and significantly defined by its difference from typicality. Brideoake writes that their relationship was celebrated by other people as a form of mourning the relationships that they could not form.
Eugene Coyle recounts that a "succession of their pet dogs were named 'Sappho'."
Lady Eleanor died at Plas Newydd on 2 June 1829, and her friend died there on 9 December two years later. They are buried with their maid, Mary Carryll, beneath a substantial neo-Gothic tombstone in Llangollen churchyard.