Prior to our current understanding, Irish historians, such as MacLysaght and Woulfe, identified two Irish Pádraig clans. They noted the Mac Giolla Phádraig (Mac Gilpatrick) Clan were ancient rulers over Kilkenny and parts of Laois and that while one branch became the Fitzpatrick Barons of Upper Ossory, there were also branches that settled in Clare, Cavan, Leitrim, and ‘other parts of Ireland’. And then there were the Ó Maol Phádraig (O'Mulpatrick), a Clan that were common in Cavan and Cork. The surname O'Mulpatrick is now extinct, but Woulfe maintained it was too numerous to have died out and was probably anglicised to Fitzpatrick.

In addition to the Irish surnames, Woulfe noted the surname Pádraig (Patrick) came to Ireland about the time of the Anglo-Norman invasion, although it was confined to Leinster.

Much of the context of the Irish Pádraig surnames referred to by Irish historians came from 1659 ‘Census’. This was not a census as such, particularly because returns for Cavan, Galway, Mayo, Tyrone and Wicklow were not included, and returns for Co. Cork and Co. Meath were incomplete. Nevertheless the ‘Census’ records the surname Fitzpatrick in Co. Kilkenny, Co. Laois, Co. Meath, Co. Kildare and Co. Tipperary. Mulpatrick is recorded in Co. Longford, Mac Gilpatrick in Co. Down, and McPatrick in Co. Antrim. The reportedly Anglo-Norman Patrick is recorded in Co. Kilkenny.

The 1901 census of Ireland is the earliest that provides robust data on the distribution of Fitzpatricks. Aside from Dublin, the five most populous counties in rank were Cavan, Laois, Down, Cork, and Clare. Due to what MacLysaght refers to as the ‘corruption of Irish surnames’ in the 17th Century, the 1901 Census ‘throws a blanket’ over all Fitzpatricks, and the origins of the Fitzpatrick surname in the counties is indiscernible. Historians, who only had the benefit of paper records, quite naturally assumed that the modern Laois Fitzpatricks were probably related to the lords of Ossory, and that Briéfne and Cork Fitzpatricks were also likely either of that branch, or perhaps the lost O’Mulpatricks. And, also unsurprisingly, some Ulster Fitzpatricks were considered by some to have planter roots.

Fast forward to the 21st Century, and DNA analysis has proven to be a powerful tool in uncovering Fitzpatrick origins and relationships. Needless to say, a complex picture has emerged.

So far at least six major and distinct Fitzpatrick septs have been identified based on genetic and historic data:

• Anglo-Normans or late arriving (ca. 500AD) Gaels (FGC5494…A1488) tracing to Co. Kilkenny, Co. Laois and Co. Tipperary;
• Briéfne Irish (FGC11134…BY9002);
• Briéfne Irish (L513);
• Leinster Irish (Z255…BY2849) tracing to Co. Kildare, Co. Louth and Co.Down;
• Munster Irish (FGC11134…CTS4466) tracing mostly to Co. Cork and Co. Kerry; and,
• Munster Norse (I-M223) tracing to Co. Clare.

DNA analysis indicates two of the septs, Briéfne Irish (FGC11134…BY9002) and Leinster Irish (Z255…BY2849), have unbroken Fitzpatrick lineages that date to the dawn of surnames in Ireland (ca. 1000 AD). Hence, DNA evidence would support any claim from both septs that they descend from the Mac Giolla Phádraig chieftains, although the Briéfne sept might, otherwise, descend from the Ó Maol Phádraigs.

The remaining four septs, and approximately 20 smaller and genetically distinct groups, have an association with the Fitzpatrick surname from ca.1300 AD and later.

Those that trace to Ossory in recent times (FGC5494…A1488) most likely descend from one of any number of Anglo-Norman lords, who were a force that decimated the region in the 13th Century, and in doing so displaced the native Mac Giolla Phádraigs. This group features close DNA matches to men with prominent Norman surnames, notably D’Alton and FitzGerald, which provides insight into the possible non-native Irish patrimony of Ossory Fitzpatricks. Alternatively the Ossorian Fitzpatricks may descend from late arriving Gaels, although there is no historic reference to such a sept. Either way there is a significant disruption of the historical Fitzpatrick narrative, i.e., that the Barons of Ossory were descendants of the Mac Giolla Phádraig chieftains.

Fitzpatrick Briéfne Irish (L513) are two distinct groups, one related to Clan Maguire and the other to Clan O’Rourke. Fitzpatrick Munster Irish (FGC11134…CTS4466) trace mostly to Co. Cork and Co. Kerry and are strongly associated with Clan McCarthy.

The aims of the Fitzpatrick One Name study are to:

Catalogue all Irish religious and civil records for Fitzpatricks.

Detail all major Fitzpatrick lineages identified from the 1911 Ireland Census and earlier, and establish their connections to Fitzpatricks living today.

Use historical records and DNA insights to gain an understanding of the origins of the main Fitzpatrick septs.

Variants in modern use are Kilpatrick, McElfatrick, McPatrick and Patrick. Older variants include Mac Giolla Phádraig, MacGilpatrick, MacKilpatrick, McElfatrick, Mulpatrick, Ó Maol Phádraig, O'Mulpatrick.

There are references to Ó Maol Phádraig of Meath in the Annals as early as the 9th Century. Variants are used right up until the 17th Century where it occurs in the Patent Roll of James I in Co. Cavan and Pender's Census (1654-1659). Mulpatrick disappears from the historic records after the 17th Century, adherents of the name took on Fitzpatrick in its place.

Fitzpatrick is more well known as a translation of the surname Mac Giolla Phádraig. Gilla Patráic mac Donnchada was a tenth century king of Ossory and his sons were subsequently styled Mac Giolla Phádraig, i.e., son of Giolla Phádraig. The Mac Giolla Phádraig surname was used in Ossory until 1541 when Brían Óg Mac Giolla Phádraig, on surrender to Henry VIII, took the surname Fitzpatrick.

The Mac Giolla Phádraigs in other parts of Ireland became known as Fitzpatricks at later stages.

Prior to its use in Ireland, Fitzpatrick is found associated with the Earls of Salisbury, England and the Patrick family of Le-Lande Patry, Normandy, both from ca. the 12^thCentury.

Much has been written about the Fitzpatricks of Ossory. Barnaby Fitzpatrick (c. 1485-1575) was the last claimant to the kingdom of Ossory (Osraige). Under surrender and regrant he was created the Baron of Upper Ossory in 1541 by Henry VIII. Fitzpatrick has remained a common surname in Counties that share the territory of ancient Osraige, viz., Kilkenny, Laois, Offaly, Tipperary and Waterford.

Fitzpatricks have long been present in Bréifne. Among the earliest records of the use of the surname is reference to the Fitzpatricks from Co. Cavan, who are recorded as supporters of Owen Roe O'Neill at the Battle of Benburb in 1646.

Early occurrences of Fitzpatrick surname pre-cursors in several Irish Counties occur as MacGilpatrick in the Patent Roll of James I. Of note are the are Mac Gilpatricks that pertain to Co. Down throughout the 17th Century. M’Illepatrick, a variant of Mac Giolla Phádraig, is listed as one of the principal names in Upper Iveagh in the 1659 Census; MacGilpatrick  ceased to be used in Iveagh in the early 18th Century when it was replaced by Fitzpatrick.

Today Fitzpatrick ranks as about the 60th most common surname in Ireland, and significant numbers of Fitzpatricks are also found in England, Scotland, the United States, Canada, Australia and New Zealand.

The surname Fitzpatrick is geographically diverse, both within Ireland and globally. Based on the Griffith's Valuation of households in the mid-1850s, 75% of Fitzpatricks in Ireland were resident as follows: County Laois (18.9%), County Cavan (14.7%), County Down (7.9%), County Cork (6.2%), County Kilkenny (6.0%), County Tipperary (5.3%), County Clare (4.0%), County Dublin (4.0%), County Kildare (3.2%), County Fermanagh (2.9%) or County Monaghan (2.7%).

A more accurate picture of the distribution of Fitzpatricks in Ireland comes from the 1901 Ireland, although an urban shift is evident: County Cavan (13.3%), County Laois (12.7%), County Down (8.2%), County Dublin (8.0%), County Cork (6.3%), County Clare (5.1%), County Kilkenny (4.4%), County Tipperary (4.4%), County Fermanagh (3.1%), County Monaghan (3.0%), County Wexford (3.0%), or County Kildare (2.9%).

Data for the Fitzpatrick One-Name Study is drawn primarily from:

Irish birth, marriage and death records to ca. 1910 (Parish and Civil);

Ireland Census records: 1901 and 1911;

England, Scotland and Wales Census records: 1841-1911;

Rental records and valuations;

Tithe Applotment book records, and; The Fitzpatrick DNA study.

There is significant genetic diversity associated with the surname Fitzpatrick. The Fitzpatrick DNA study has identified several major Fitzpatrick groups that are genetically unrelated prior to ca. 2500 BC. This accounts for approximately 50% of the DNA study members. About a further 25% fall into small groups of unknown origin, and the remaining 25% have not yet found matches within the study - although some have had success with matches on other surname projects.

The Y-DNA results of the Fitzpatrick surname project are found at FTDNA's Fitzpatrick Project.

The Fitzpatrick Clan Society, their Forum and their Facebook Page.