Composition for dyeing the hair, comprising a heterocyclic oxidation base and a 2-amino-5-ethylphenol coupler The present invention relates to a composition for dyeing keratin fibres, comprising a particular heterocyclic oxidation base and a 2-amino-5-ethylphenol coupler. The invention also relates to a process for dyeing keratin fibres using this composition. Finally, the invention relates to the use of such a composition for dyeing keratin fibres, and in particular the hair.