The funeral is taking place of Barney McGinley, who was killed as part of an alleged Traveller feud in Co. Fermanagh last week.
Security is tight in Athlone, with up to 100 gardaí involved in policing the funeral.
Mr McGinley is survived by his wife Brigid, nine children and 49 grandchildren.
Hundreds of mourners have gathered at St. Mary’s church in Athlone this afternoon to remember Barney McGinley.
Floral tributes festoon the church remembering the 63-year-old as a father and grandfather. Fr. Simon Cadden, a family friend from Granard, paid tribute to Mr McGinley as a family man.
"Barney was a very proud, happy, contented man - never wanted for much out of life , just simple, quiet pleasures … Barney's life was his family, it meant more to him for anything," he said.
The 63-year-old was attending a family wedding in Newtonbutler in Co. Fermanagh last Wednesday when he was shot – he died from his injuries a short time later.
It is alleged the shooting was as a result of an ongoing feud within the Traveller community.
Fr. Turlough Baxter, chief celebrant for the requiem mass, urged those involved in violence to turn away from it.
"It takes a short time to open wounds in others that can take a lifetime to heal. Violence can never be the answer, because all it does is foster more hurt and violence," he said.
Security is tight in Athlone this afternoon – for fear of reprisals, with one garda estimate putting the number of gardaí policing the funeral at 100.
Garda checkpoints have been set up on roads leading into Athlone, with uniformed gardaí and members of the armed response unit outside the church.
The PSNI and Gardaí are working together on the ongoing investigation.