A process for the recovery of sulphur from gaseous stream containing hydrogen sulphide in a percentage of from 5 to 30% by volume, that consists of: 1) two combustion steps carried out in two separate zones of a Claus thermal reactor on the gaseous stream containing hydrogen sulphide, a fuel and air and/or oxygen, said gaseous stream being distributed between the two zones in such a way that in the first zone oxygen is lacking, wherein 1 a) the first combustion step, made in the first zone at a temperature equal or higher than 950°C, is a partial combustion of the gaseous stream containing hydrogen sulphide to promote the formation and the retention of reducing compounds, like hydrogen and carbon monoxide, the production of the reducing compounds occurring by reaction of the gaseous stream containing hydrogen sulphide and other pollutant substances, with a sub-stoichiometric quantity of air and/or oxygen, in the presence of suitable fuel quantities, according to the reactions, and, H 2 S ← -------- → H 2 + S CH 4 + H 2 O ← ------- → CO + 3 H 2 O CO + H 2 O ← ------ → CO 2 + H 2 1b) the second combustion step, made in the second zone, is a combustion of the gaseous stream containing hydrogen sulphide, according to reaction H 2 S + 3/2 O 2 ← --- → SO 2 + H 2 O, 2) one or more catalytic stages, according to the Claus process, wherein the hydrogen sulphide and the sulphur dioxide present in the gas obtained in the previous stage react according to the Claus reactions and H 2 S + 3/2 SO 2 ← --- → SO 2 + H 2 O, 2H 2 S + SO 2 ← ----- → 2H 2 O + 3/n S n 3) a catalytic stage wherein the sulphur compounds contained in the Claus process tail gas, coming in contact with the reducing gases formed in the initial stage of partial combustion of the process, are reduced to hydrogen sulphide according to the reaction and SO 2 + 3H 2 ← ---- → H 2 S + 2H 2 O S + H 2 ← ---- → H 2 S 1) two combustion steps carried out in two separate zones of a Claus thermal reactor on the gaseous stream containing hydrogen sulphide, a fuel and air and/or oxygen, said gaseous stream being distributed between the two zones in such a way that in the first zone oxygen is lacking, wherein 1 a) the first combustion step, made in the first zone at a temperature equal or higher than 950°C, is a partial combustion of the gaseous stream containing hydrogen sulphide to promote the formation and the retention of reducing compounds, like hydrogen and carbon monoxide, the production of the reducing compounds occurring by reaction of the gaseous stream containing hydrogen sulphide and other pollutant substances, with a sub-stoichiometric quantity of air and/or oxygen, in the presence of suitable fuel quantities, according to the reactions, and, H 2 S ← -------- → H 2 + S CH 4 + H 2 O ← ------- → CO + 3 H 2 O CO + H 2 O ← ------ → CO 2 + H 2 1b) the second combustion step, made in the second zone, is a combustion of the gaseous stream containing hydrogen sulphide, according to reaction H 2 S + 3/2 O 2 ← --- → SO 2 + H 2 O, 1 a) the first combustion step, made in the first zone at a temperature equal or higher than 950°C, is a partial combustion of the gaseous stream containing hydrogen sulphide to promote the formation and the retention of reducing compounds, like hydrogen and carbon monoxide, the production of the reducing compounds occurring by reaction of the gaseous stream containing hydrogen sulphide and other pollutant substances, with a sub-stoichiometric quantity of air and/or oxygen, in the presence of suitable fuel quantities, according to the reactions, and, H 2 S ← -------- → H 2 + S CH 4 + H 2 O ← ------- → CO + 3 H 2 O CO + H 2 O ← ------ → CO 2 + H 2 1b) the second combustion step, made in the second zone, is a combustion of the gaseous stream containing hydrogen sulphide, according to reaction H 2 S + 3/2 O 2 ← --- → SO 2 + H 2 O, 2) one or more catalytic stages, according to the Claus process, wherein the hydrogen sulphide and the sulphur dioxide present in the gas obtained in the previous stage react according to the Claus reactions and H 2 S + 3/2 SO 2 ← --- → SO 2 + H 2 O, 2H 2 S + SO 2 ← ----- → 2H 2 O + 3/n S n 3) a catalytic stage wherein the sulphur compounds contained in the Claus process tail gas, coming in contact with the reducing gases formed in the initial stage of partial combustion of the process, are reduced to hydrogen sulphide according to the reaction and SO 2 + 3H 2 ← ---- → H 2 S + 2H 2 O S + H 2 ← ---- → H 2 S