Answer
The successor to Éamon de Valera as Taoiseach was Seán Lemass who governed Ireland as the second Taoiseach, serving in this capacity from 1959 to 1966. Lemass implemented numerous socio-economic reforms during his tenure, fostering Ireland's transformation from a primarily agricultural nation to a contemporary industrialised economy. His initiatives paved the way for rapid economic growth and modernisation within the country during that period.