Iconic landmarks including Christ the King in Almada, the Duke of Terceira statue in Lisbon and the Condes de Castro Palace Museum in Cascais were all cast a green tinge as part of the Irish celebration, which falls on 17 March.
Christ the King and the Duke remained green until Wednesday, while the palace in Cascais will keep its new colour until this Saturday.
Other landmarks around the world that were also bathed in green to mark the date included the London Eye, Paris’ Sacred Heart, the leaning Tower of Pisa and the Burj Al Arab hotel in Dubai.