Police found the 24-year-old outside the house in Rhode, County Offaly, at 01:50 local time on Monday after a neighbour raised the alarm.
Irish broadcaster RTÉ said the man was stabbed up to 16 times and sustained severe burns to 90% of his body.
It said police were treating the attack as attempted murder.
The victim was initially taken to the Midlands Regional Hospital in Tullamore, County Offally, but has since been transferred to St James's Hospital in Dublin.
Officers have been carrying out house-to-house inquiries and have set up an incident room at Tullamore police [Garda] station.
A man who was found with stab wounds and extensive burns at the scene of a house fire in the Republic of Ireland is critically ill in hospital.