Beta-haemoglobinopathies are amongst the most common genetic disorders worldwide, with over 7% of the world’s population carrying a haemoglobin mutation and approximately 300,000 affected births every year. Sickle cell disease and beta-thalassaemia are caused by mutations to the adult beta-globin gene. As current therapeutic options carry various limitations, reactivation of the developmentally silenced foetal gamma-globin gene is an attractive therapeutic option as it leads to elevated foetal haemoglobin levels and alleviates the symptoms of beta-haemoglobinopathies. The continued expression of foetal haemoglobin into adult life occurs in a natural condition called the Hereditary Persistence of Foetal Haemoglobin (HPFH). Point mutations in the proximal promoter of the foetal gamma-globin gene can cause HPFH. The -113 A>G HPFH mutation falls within the -115 cluster of HPFH mutations, a known binding site for the transcriptional repressor BCL11A. We demonstrate that the ‑113 A>G HPFH mutation, unlike the other HPFH mutations in this cluster, does not disrupt the binding of BCL11A, but rather creates a de novo binding site for the transcriptional activator GATA1. The introduction of the -113 A>G HPFH mutation into an erythroid cell line, using CRISPR/Cas-9 technology and homology directed repair, leads to increased GATA1 binding and elevated foetal gamma-globin levels. These results reveal the mechanism by which the -113 A>G HPFH mutation operates to elevate foetal haemoglobin and highlights how naturally occurring mutations in the foetal globin proximal promoter not only disrupt repressor binding sites but here creates a de novo binding site for an erythroid activator.