75 complaints from Co Mayo were lodged with the Ombudsman's Office last year.
The Office examines complaints from people who feel they're unfairly treated by organisations that deliver public services.
The annual report for 2018 shows the Ombudsman received a total of 3,364 complaints in 2018 - with 75 from Mayo, 52 from Roscommon, 44 from Sligo and 236 from Co Galway.
Overall, 31% of complaints related to Government Departments - with the Department of Social Protection and Revenue Commissioners topping the listd.
26% of complaints related to Local Authorities, and 21% involved health and social care - these included complaints about hospitals, primary and community care and disability services.
Complaints about the HSE were mostly related to medical cards, the Fair Deal nursing home scheme and drugs payment scheme