The teenagers, one believed to be just 15, approached the youth on the pretence of selling perfume before attacking him.
One of the teenagers sprayed the victim with a liquid and the other set him alight before fleeing.
The incident happened just before midnight on Saturday night as the youth walked home in the Doughiska area of Galway city.
“It was an unprovoked attack which resulted in serious injuries to this young man,” said a Garda spokesperson.
The 15-year-old attacker is about 5ft 6in in height, of stocky build with red hair and freckles.
The other attacker, believed to be around 19, is 5ft 7in in height and was wearing a dark jacket to the waist with a hood pulled up.
The youth who was injured in the incident was discharged after being treated for his injuries at University Hospital Galway.
The youth suffered neck and facial burns.
It is believed he is not Irish and he lives on the east of Galway city.
The Mayor of Galway, Cllr Padraig Conneely, described the attack as “a new low” and called for extra Garda resources to be deployed in the area.
The Doughiska area has become densely populated in recent years with a large percentage being non-national.
“It is frightening to think that this could happen to a young man on his way home, minding his own business and he gets set upon for no reason.
“There seems to be no motive for the attack and this young man would appear to have been in the wrong place at the wrong time.
“The youngsters who did this need to be apprehended and brought to justice,” said Mr Conneely.
“We do not have enough gardaí on duty, but these young thugs cannot be allowed think they can carry out this sort of attack and get away with it.
“Great efforts have been made to create a new community in that area and a lot of hard work is being done and the last thing we need is the likes of these sort of attacks taking place,” said the mayor.
Gardaí at Mill Street (091-538000) have appealed for assistance.