The main cause of the Irish Potato Famine in the 19th century was the dependence on the potato as a staple food crop, particularly in the diet of the Irish population. In the late 1840s, a devastating potato blight known as Phytophthora infestans wiped out a significant portion of the potato crop, leading to widespread famine. The British government's inadequate response exacerbated the crisis, as export policies continued while the Irish faced starvation. Approximately one million people died from hunger and related diseases, while another million emigrated, leading to a profound and lasting impact on Irish society and demographics, as well as on Ireland's relationship with Britain.