Catherine Brigid Cronin (née Kiernan; 26 January 1893 – 25 July 1945) was an Irish woman widely known as the fiancée of Irish revolutionary leader and Chairman of the Provisional Government, Michael Collins.

Catherine Bridget "Kitty" Kiernan was born on 26 January 1892 in Granard, County Longford to Peter Kiernan and Bridget née Dawson. She was educated at Loreto Convent, County Wicklow. Hers was a very comfortably-off merchant family with five sisters and one brother. Her parents enjoyed a happy marriage, and life in the Kiernan home was joyous until Kitty reached her teens. On 27 November 1907, her sister, Elizabeth Mary (a twin), died aged eighteen of pulmonary tuberculosis, while Elizabeth's twin sister, Rose, would seem to have died the same year in Davos, Switzerland; which is consistent with tuberculosis as a cause of death. Her mother Bridget died on 29 November 1908, of apoplexy, while her father, Peter, died almost exactly a year later, on 9 November 1909, of pneumonia. The Kiernan family owned the Greville Arms Hotel in the town, as well as a grocery shop, a hardware store, a timber and undertaking business and also a bar. Around the corner from the hotel they operated a bakery which supplied the town and most of the surrounding countryside. All the family worked in one capacity or another.

Michael Collins, one of the principal founders of the independent Irish state, was introduced to the vivacious Kiernan sisters by his cousin Gearóid O'Sullivan, who was already dating Maud Kiernan. Collins initially fell for the captivating Helen Kiernan, but she was already engaged to someone else. He then turned his interests to Kitty, who had already captured the interest of Collins' friend Harry Boland. However, it was Collins to whom Kitty became engaged, with plans to marry Collins in a November 1922 double ceremony to include the nuptials of Maud and Gearóid. Collins' assassination four months earlier resulted in a single wedding taking place.

On 10 June 1925, Kitty married Felix Cronin, who was Quartermaster General in the Irish Army. They had two children, their first born son, Felix Junior (d. 21 November 1999), and their second son, Michael Collins Cronin (b. 20 December 1929, d. 5 January 2021).

Kitty died, aged 54, of a cerebral hemorrhage on 24 July 1945, and her grave is close to that of Collins. Felix Cronin died suddenly on 22 October 1961 while playing golf at Woodbrook Golf Club and is also buried in Glasnevin. Felix Junior and his son Rex (d. 25 November 1986, aged 23) are interred with his parents Kitty and Felix in Glasnevin Cemetery. As of 27 April 2024, Michael Collins Cronin is also interred at the family's plot in Glasnevin.

Several sources, for example, a 1996 piece from the Irish Times entitled "Life after Mick", state that Kitty Kiernan plus several of her siblings died of Bright's disease; what one would class today as chronic nephritis. Her sisters Maud (2 October 1895–28 October 1940) who married Gearóid O'Sullivan on 18 October 1922 and Helena Josephine (22 September 1894–28 May 1940) who married solicitor Paul McGovern on 5 October 1921 both have chronic nephritis registered as their cause of death. While the cause of death for Kitty is registered as a cerebral hemorrhage, the suggestion is that she suffered from ill-health for several years before her death.

Her only brother, Laurence Dawson Kiernan (22 Jan 1892–22 December 1948), of the Greville Arms Hotel, died of cirrhosis of the liver.

Her twin sisters, Lizzie and Rose, both died in 1907 of tuberculosis.