Catherine Day (born 16 June 1954 in Mount Merrion, Dublin) is a former European civil servant from Ireland.
Appointed in November 2005 as Secretary-General of the European Commission,[1] she served two terms with President Jose Manuel Barroso and continued with his successor, Mr Jean-Claude Juncker until she retired in September 2015.
During her term of office she developed the role of the secretariat-general in cross-commission policy co-ordination, its better regulation and impact assessment/policy evaluation approach and was a key negotiator of the 2014-2020 multi-annual financial framework for the EU budget.
She also led the commission's work on the European Semester, co-ordinating EU and national economic and social policies.
From 2017 to 2019, Day chaired an independent review group on the role of voluntary organisations in publicly funded health services in Ireland.