O’Mahony guided Galway to two All-Ireland titles in 1998 and 2001 and is one of the few managers to win provincial titles with three different counties, his own Mayo and Leitrim in their landmark 1994 success, in addition to Galway.
He was 70 and had been battling cancer in recent years.
O’Mahony, from Ballaghdereen, played with Mayo and won an All-Ireland U-21 title in 1974 as a corner-back before managing them to another All-Ireland title at the grade nine years later when he was just 30.
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By then his three-year playing career with Mayo had long since ended, having been left off subsequent squads after the 1975 Connacht final replay loss to Sligo.
O’Mahony took to management and coaching easily, having been involved with teams in St Nathy’s in Ballaghaderreen where he was a teacher.
Whatever team he took charge of he invariably improved, some beyond all expectations.
He took over the Mayo senior team for the first time in late 1987 and within 10 months had guided them to a Connacht title. In the All-Ireland semi-final, they almost dethroned Meath, having come late to hit the champions with two goals.
A year later Mayo won another Connacht title under his direction and reached an All-Ireland final for the first time since 1951, losing to Cork.
He spent another two years with Mayo but stepped down after a dispute over his freedom to choose his own selectors.
Leitrim quickly courted him however and after winning an All-Ireland B title in 1990 there was promise there.
He took charge there for the 1992-1993 season, at the invitation of then Leitrim chair Tony McGowan and that promise was evident when they beat Galway in the 1993 Connacht Championship.
The following year they beat Roscommon, Galway and Mayo, in the final, to win their first provincial title in 67 years and their only one since.
It was a magnificent and emotional achievement, captured brilliantly by the late Micheál O’Muircheartaigh at the end when he declared that “there will be many a Leitrim man looking down from the veranda of heaven right now.” They subsequently lost an All-Ireland semi-final to Dublin.
He was a manager and coach generally considered ahead of his time for the level of detail he put into preparation, especially analysis of opponents. His knowledge of football and footballers across the country was extensive, helped by his library of old match videos that he delved into for further insight before more modern analysis techniques were available.
In 1997 he took over from Val Daly as Galway manager, quite the move at the time for a former Mayo player and manager. He made an instant impact though, winning a Connacht title and then an All-Ireland title with one of the great second half displays against Kildare. It was Galway’s first All-Ireland title since 1966.
Merging the talents of younger players like Padraic Joyce, Michael Donnellan and John Divilly with more seasoned players like Kevin Walsh, Tomás Mannion and Jarlath Fallon, O’Mahony was able to extract the best out of them to contest two more All-Ireland finals, 2000 when they lost to Kerry after a replay, and 2001 when they came from behind to again deliver a second half tour de force against Meath.
He won further Connacht titles with Galway in 2002 and 2003 and brought his involvement to an end after the 2004 championship ended in the qualifiers.
Three years later he was back in Mayo for a second spell, replacing Mickey Moran and John Morrison who had managed them to the 2006 All-Ireland final.
O’Mahony’s second spell wasn’t as successful however with just one Connacht title in 2009. In his final year Mayo played just two championship games, losing to Sligo and Longford.
By then he was a Fine Gael TD for Mayo, having been elected at the first attempt in 2007, an election that took place in the middle of the championship that year. He spent the next nine years as a TD and a further four years as a senator.
His desire to be involved with football teams was undimmed, even in those years. He had advisory roles with Carlow and Leitrim and up to last year was manager of Salthill-Knocknacarra in Galway, taking them to the 2022 Galway final which they lost by a point to Maigh Cuilinn.
One of O’Mahony’s great friends was former RTE correspondent Tommie Gorman who only died last week, having battled cancer himself for many years.
The pair struck up a friendship when O’Mahony began supplying local notes to a newspaper in the west of Ireland that Gorman had been involved with. Gorman did video analysis in O’Mahony’s early years as a manager.
He can undoubtedly considered one of the GAA’s greatest managers given the breadth of his achievements but beyond that success O’Mahony will be remembered as a most courteous, engaging and decent person and consequently enjoyed widespread popularity, not just among former players he managed but constituents he served and everyone he was connected with.