Martin Callinan was a member of An Garda Síochána for 41 years and commissioner for just over three years.
He was due to retire on age grounds when he reached 60 last August but was offered an extension by the Government to continue for a further two years. He was set to retire in August 2015.
The married father of three is from Glasnevin, north Dublin, and was appointed by government to the post of commissioner in December 2010.
He was the first Dubliner in the 82-year history of the force to be appointed Garda Commissioner.
Minister for justice Dermot Ahern nominated Mr Callinan for promotion saying he had a "distinguished record of service in the Garda Síochána, with a wide range of experience in key positions in the force, and has all the qualities needed to lead the Garda Síochána successfully through the challenging times ahead".
He succeeded Fachtna Murphy, who retired on age grounds after, like Callinan, availing of an extension to continue serving despite reaching retirement age. Callinan was at the time of his promotion one of two deputy commissioners; the second-highest rank in the force.
Head of operations
In his previous role, Callinan was head of operations across the force, meaning he was in charge of all operational policing in the Republic.
In that post he also had overall responsibility for anti-terrorism operations and all national Garda units, including the Garda National Drugs Unit, Criminal Assets Bureau and Organised Crime Unit.
The six regional assistant commissioners and the assistant commissioners in crime and security, national support services and traffic were also under his command when he was a deputy commissioner.
He was a member of the force for 13 years before being promoted from a rank-and- file garda to sergeant.
And it was when he moved back to Dublin after spells in the regions that he worked on a number of very high-profile cases, including being a detective sergeant in the Tango Squad that conducted round-the-clock surveillance of gang leader Martin Cahill.
He was also the lead officer in investigating the Real IRA, which was behind the Omagh bombing. He headed the Garda reviews carried out following the Murphy and Ryan reports into clerical child sex abuse.
He was involved in the investigation of the 1996 murder of Veronica Guerin when an inspector in the National Bureau of Criminal Investigation and was also involved in the searches for the bodies of those "disappeared" by the IRA.
Callinan assumed control of the Garda when the record 14,500 strength of the force was just about to begin falling because of the recruitment ban.
It has now dropped to 13,000 just as new recruits are about to start entering training, for the first time in five years.
Fall in reported crime
Crime had begun to fall when he was appointed commissioner and almost all crime categories have continued to show significant falls during his stewardship.
Road deaths also reached record lows during his term but have begun to increase slightly of late.
Callinan joined An Garda Síochána in 1973 and in his early years served in Waterford, Blanchardstown, Cabra, the former central detective unit, Pearse Street, Terenure, Swinford and the crime and security section at Garda Headquarters in Phoenix Park, Dublin.
He was appointed assistant commissioner in 2005 and in January 2007 became a deputy commissioner.
He holds a BA in police management. In 1995 he undertook management training at the FBI Academy in Quantico, Virginia, where he also recently completed the national executive institute programme designed for police chiefs from around the world.
In his spare time he is a keen golfer.