However, prison sources say the reality is the lines between the different gangs have become so blurred, with the influence of the Kinahan cartel so all pervasive, the traditional divides can no longer be said to apply.
Five prisons, in particular, house the majority of the country’s most notorious gangland criminals.
These are Mountjoy, Portlaoise, Wheatfield, Castlerea and Limerick.
Mountjoy and Portlaoise have become the major accommodation hubs for criminals linked with the Kinahan faction, while Wheatfield has been used – since the fallout of the Regency Hotel shooting – to house the Hutch crew – and, most notably, in recent months Gerry ‘the Monk’ Hutch.
This week, following an extensive investigation by the Sunday World, we break down the gangs active inside Ireland’s jails and trace the alliances and enmities that prison officers bravely confront and police on a daily basis.
Kinahan Cartel-linked gangsters are now the undisputed controlling force within the criminal population in Mountjoy Prison.
Backed up by Eastern European muscle provided by Polish cage-fighter Leszek Sychulec and a number of the killer's countrymen - Kinahan gunman Trevor Byrne, gang quartermaster Graham Gardiner, hitmen Glen and Gary Thompson and former British Army soldier Robert Brown run the facility's C-Wing.
Other high-profile inmates linked to the cartel include money launderer Graham 'the Wig' Whelan, and Glenn Holland, who is serving six-and-a-half years for possession of guns and drugs.
The gang's ranks behind bars in Mountjoy also include Declan 'Mr Nobody' Brady, who is being housed in the prison's Progression Unit.
Cartel criminals control the flow of drugs into the prison and were responsible for the largest-ever consignment of contraband smuggled into an Irish prison in a food truck two years ago.
Criminals linked to drug dealer 'Mr Flashy' are considered as a 'sub-crew' to the Kinahans in Mountjoy.
These include brothers Scott and Mark Capper.
Scott Capper is considered the right-hand-man and a key enforcer on the outside for the Finglas drugs boss nicknamed 'Mr Flashy'.
Sources said this week that the 27-year-old, who was sentenced to two-and-a-half years in prison last July for stealing a €50,000 cashbox from a security guard, mixes freely with the Kinahan inmates, who treat him as one of their own.
The same goes for his brother Mark who, according to sources, despite pulling out of a bid to whack Gerry Hutch's brother Patsy two days before the 'hit' was due to go down, has gotten a pass from the Cartel.
Mountjoy is also home to Limerick criminals Wayne and Dessie Dundon, who are housed on protection on B-Division.
Despite being under lockdown, convicted killer Wayne is suspected by prison officers of being responsible for the large-scale smuggling of contraband phones into the prison.
Brother Dessie - who is hoping to be moved to an open prison in the near future - works as a landing cleaner on 'B'.
Two members of the notorious Wilson clan are also incarcerated in Mountjoy.
Hitman Keith Wilson has served 12 years in the 'Joy for the murder of Real IRA member Daniel Gaynor in August, 2010. He is now housed in Mountjoy's Progression Unit.
Nephew Luke Wilson is serving 11 years in prison - and two more for attacking a prison officer - for his part in the botched conspiracy to murder Kinahan Cartel target Gary Hanley in 2017.
Castlerea Prison is currently home to the criminal dubbed by prison officers as 'The West's Mr Big'.
This man cannot currently be named as he is before the courts on serious charges relating to gangland crime.
Sources said the criminal who is on the prison's A-Wing controls the drug trade in Sligo and the surrounding counties.
He has forged strong alliances with the Maguire faction in Drogheda, the Dublin drug-boss 'Mr Big' and the Limerick gangs.
Earlier this week, a phone was found in possession of a man the druglord shares a cell with.
Sources say it is suspected the phone belonged to him.
Limerick thug Nathan Killeen is housed on the A2 landing and is considered to be close to the Sligo kingpin.
Killeen is serving a life sentence for his role in the murder of businessman Roy Collins in 2009 on the orders of gang boss Wayne Dundon.
His fellow county man and killer, Anthony 'Noddy' McCarthy is housed in the Grove in Castlerea.
He was sentenced to 19 years for his part in the infamous murder of rival mob boss Kieran Keane, that set off a decade-long gangland feud in the city.
The jail also has a Kinahan presence in the form of gun-for hire Caolan Smyth - who was moved there from Cork last month to serve out his 20-year sentence for the attempted murder of James 'Mago' Gately.
Castlerea also houses inmates linked to different Traveller gangs from all over the country, but a source said: "If the Traveller criminals in Castlerea could be said to have a boss then it is Michael Quinn McDonagh.
"Nothing happens among the Travellers in the prison without him giving it the okay."
Bareknuckle boxer Quinn McDonagh was sentenced to life in 2015 after he pleaded guilty at the Central Criminal Court to beating to death his partner Jacqueline.
Traditionally, the prison where Republican inmates were housed, the State's only maximum-security prison is now also being used to house Cartel criminals and border crime gangs.
The Kinahan inmates in Portlaoise are housed on A-Block and C-Block. The most senior Kinahan Cartel figures on A-Block are Lee Canavan, who was jailed for life for the murder of Daithi Douglas in May of 2021 and is also a suspect for the brutal Gary Hutch killing in Spain, and a second Cartel killer who cannot be named as he is currently before the courts on separate serious charges.
Garda killer Aaron Brady, who is under the protection of the Cartel inmates, is also locked up on A-Block.
The block is also being used to house bandit brothers Stephen, Gerard and Ciaran Duffy, who are serving sentences relating to ATM raids along the Border.
On C-Block, Cartel associates include Peadar Keating and David Duffy.
Keating is one of the most senior members of the Kinahan mob to be jailed.
He received an 11-year sentence for directing the failed murder attempt on Hutch associate James 'Mago' Gately in 2017.
The plan was foiled when Estonian hitman Imre Arakas was arrested and a weapon seized after he travelled to Ireland for the 'hit'.
David Duffy, meanwhile, is serving five years for his role in the plot to kill Gately.
He booked flights for Arakas to come to Ireland.
C-Block is also home to disgraced millionaire playboy Jim Mansfield.
Despite being under investigation by the Criminal Assets Bureau (CAB) in relation to a €4.5 million payment from the Kinahan Cartel, Mansfield Jnr is not under threat and mingles freely on the block.
Mansfield (54), of Tassagart House, Garters Lane, Saggart, Co. Dublin, is currently serving an 18-month sentence for ordering the destruction of CCTV footage showing him with his former employee, Martin Byrne, on the morning the latter was kidnapped by republican terrorists Dessie O'Hare and Declan 'Whacker' Duffy.
E-Block houses republican inmates and is now suspected of being the route through which contraband drugs and phones enter the prison.
Last month, the republican prisoners expelled a long-term inmate - who is serving a lengthy sentence in connection with explosives - from the block after blaming him for bringing in a consignment of drugs and phones found in a food trolley.
Drugs continue to flow into Limerick jail where the prison wings are to this day divided up along traditional lines.
A-Wing houses Kenneth Collopy, who is serving a life sentence for shooting dead innocent carpenter Daniel Fitzgerald in December 2009.
Collopy is now the only senior member of the Collopy faction left behind bars, although he was joined by Tony Collopy - the son of heroin dealer Kieran Collopy - in November, when the younger man was jailed for two-and-a-half-years for tasering a man during a drunken row.
B-Wing houses the remnants of the McCarthy-Dundon gang alongside other prisoners, while C-wing is mixed.
Sources said the drug flow into the prison is still controlled by criminals associated with the Collopy, McCarthy-Dundon and Keane factions. But, the Collopys are 'top dog' when it comes to smuggling contraband into the facility.
The main route for drugs into prison is through new inmates - who, sources say, 'are stuffed like turkeys' prior to court appearances where they know they are going to be incarcerated.
"The situation in Limerick is very fluid and although it's no longer the case that all the individual groups can be placed in one camp or another - the old gangs are still very much in operation at the top of things."
Following the eruption of the State's bloodiest-ever gangland feud between the Hutch and Kinahan crime groups, a decision was made to house all Hutch- affiliated criminals at Wheatfield Prison, in a bid to isolate and protect them from the long reach of the Cartel.
Alan Hutch - who served a sentence for threatening to kill three gardaí - was moved from Mountjoy's Training Unit to Wheatfield where relative Derek 'Del Boy' Hutch was already serving a sentence for manslaughter.
Both have since completed their sentences unharmed.
Convicted torturer Jonathan Dowdall - who is separately before the Special Criminal Court charged with the Regency Hotel murder of David Byrne - also completed his sentence for false imprisonment and threats to kill as did his dad Patrick who now faces a charge of facilitating the murder at the Regency.
In their place, the prison now houses the Cartel's number one target throughout the feud, Gerry 'The Monk' Hutch.
Hutch, who was extradited back to Ireland from Spain last year, is incarcerated on the prison's G3 landing where it is thought, if convicted of the murder of David Byrne, he will serve out a life sentence - unless he secures permission to serve out the sentence in Spain.
In recent years, the Midlands Prison has increasingly been used to house sex offenders - while more volatile inmates have either been dispatched to the State's other jails or have served out their time.
Only a few remain and these are primarily of Limerick origin.
One of the last of the so-called big hitters 'Fat' John McCarthy was released last August after serving 14 years for possession of heroin.
He left behind him in the jail David 'Frog Eye' Stanners and Christie 'Smokie' Costelloe, who are both serving life for the murder of Kieran Keane. n