611,000 people are now on the list, while almost 145,000 of these have been waiting at least 18 months for an appointment.
According to data from the National Treatment Purchase Fund, the list grew by nearly 10,000 between July and August.
There has been warning about a new crisis in Irish hospitals this winter, as waiting lists have reached this record high.
Dr Denis McCauley of the Irish Medical Organisation says the new record is largely due to Covid-19 measures in hospitals.
“I do accept that going forward there will have to be certain reduced capacity which will have an effect, but I do wish that they would reach that reduced capacity as quickly as possible,” he said.
“I do not think that has been achieved yet and unless they maximise the work that they can do in the medium term, these will unfortunately lengthen.”
Urgent action
Over 841,000 people are currently on some form of hospital waiting list, according to the National Treatment Purchase Fund.
The new figures also show 77,600 people were waiting for an inpatient procedure last month.
Sinn Féin's health spokesperson, David Cullinane, says urgent action is needed.
“This is quite serious, and we’ve been saying for some time we are facing into a winter in our acute hospitals like we have never seen before,” he said.
“They face an unprecedented challenge, and unless we can put the resources in very, very quickly, we’re going to see these numbers increase week by week and obviously that’s on the watch of Minister Donnelly and he needs to act very quickly and very urgently.”
