The valve-controlled ignition pre-chamber (1) is intended for an internal combustion engine (2) which has a combustion chamber (5) in which a main charge (30) more less diluted with a neutral gas is ignited, said prechamber (1) comprising a stratification cavity (6) into which ignition means (11) open and into which a stratification injector (8) can inject a pressurized readily-inflammable pilot charge (9), a stratification valve (13) being able to close off the stratification duct (7) in full or in part, notably under the effect of the pressure of the gases obtaining in the combustion chamber (11).