Brophy is an Irish surname of ancient origin, which is derived from the Irish "Uí Bhróithe" or "Ó Bróithe" septs that were located mostly around Ballybrophy, Laois, and in counties Carlow and Kilkenny. The family has been prominent in the history of Ireland for nearly 1000 years and has included petty kings (Rí), clerics, soldiers, and writers. The family was first mentioned in the late 11th century, but as a member of the Dál Birn dynasty, its semi-legendary genealogy stretches back to AD 200 according to the Bodleian Library, MS Rawlinson B 502. As such, it remains one of Ireland's oldest extant pre-Norman Conquest noble families.

The ancestral seat of the family chief became Ballybrophy (from Irish: Baile Uí Bhróithe, meaning 'townland of Ó Bróithe') after the Norman Invasion of Ireland in the 12th century.

Giolla na Naomh Ó hUidhrín wrote in the 14th century that the earliest ancestor of the Brophys was Sedna, the great-grandson of the semi-legendary pre-Christian founder of the Kingdom of Ossory, Óengus Osrithe.

In The Book of Rights, the Osraige are labeled as Síl mBresail Bric ("the seed of Bresail Bric") after Bressail Bricc, a remote ancestor of the Ossorians. Bressail Bricc had two sons; Lughaidh, ancestor of the Laigan, and Connla, from whom the Ossorians sprang, through Óengus Osrithe. Thus, the people of Osraige were also sometimes collectively referred to as Clann Connla.

"The Annals of the Four Masters'' records the death of Gilla Molua O'Brophy (Ua Bruaidheada) of Rath Tamnaighe (Lisdowney, Kilkenny) in 1069. The "Annals of Ulster" mentions that Connor O'Brophy (Conchobar Ua Broighthe), King of Ceann Chaille, and Domhnall Mac Gilla Patraic, King of Upper Ossory, were slain by the O'Moores in 1165. Giolla na Naomh Ó hUidhrín mentions the O'Brophys as residing in Magh Sedna (the Plain of Sedna) in the barony of Galmoy (barony), Kilkenny in his 14th century work, "Tuilleadh feasa ar Éirinn óigh." The name of Galmoy (barony), in Irish Gabhalmhaigh, means "plain of the Branch, or Ghabhal" (River Goul). Magh Sedna Was also known as Aos-Chinn-chaille, i.e., [the territory of] the people of Cean Chaille.

Magh Sedna is a fertile part of Ireland which the Danes invaded in the ninth century, and where the Normans came after they had conquered Britain in the eleventh century. Over the years the Norse, Norman and Gaelic bloods have mingled in the families of later centuries. It is the paradoxical story of Ireland that the conquered frequently absorbed their conquerors through intermarriage, language and customs. Hence the oppressors of one generation often produced the rebels of a later one.

William O'Brothe was appointed Prior of the Augustinian Monastery of St. Tigernacius of Aghamacart by Pope Sixtus IV on 31 March 1481. William is likely to have been the illegitimate son of Philip O'Brothe, Abbot of Kilcooley Abbey, whom Pope Pius II legitimized and instructed to be taken on as a monk at the Abby after his father's death.

When Florence Fitzpatrick, 3rd Baron Upper Ossory, the son of the last person to have claim to the kingship of Osraige, was pardoned by Queen Elizabeth I in 1601, his kinsmen, the Brophys and other "old tribesman of Upper Ossory," were also mentioned in the pardon. Ui Broithe was anglicized as O'Broghie in the Patent Rolls of James I in 1603 and 1607. The name appears as Brohy in the census of 1659.

Around 1830s the Tithe Applotment Books record 526 Brophys as holding land and so subject to tithes to the Protestant Church of Ireland. By the mid 1800's Griffiths Valuation lists 1106 Brophys renting or owning land. The 1901 Irish census lists 1818 Brophys and that grows to 1860 ten years later in the 1911 census. The distribution of Brophys in Ireland still reflects their ancient homelands concentrated in the Counties of Laois, Kilkenny and Carlow.