Ana Maria Guerreiro Dias (born January 15, 1974 in Faro, Algarve) is a Portuguese long-distance and marathon runner. She is a four-time Olympian, and a multiple-time national record holder for the long-distance running (5000 metres, 10,000 metres, half-marathon, and marathon). She also set a personal best time of 2:28:49, by finishing fourth in the women's race at the 2003 Berlin Marathon.