Pilar Geijo (born 19 September 1984 in Buenos Aires) is a world-class marathon swimmer from Argentina who trains under Diego Tricárico at Club River Plate. She has dominated the FINA Open Water Swimming Grand Prix circuit during her career and won the overall FINA Open Water Swimming Grand Prix professional circuit in 2010, 2011, 2014, 2015 and 2019. She was second in the FINA Open Water Swimming Grand Prix circuit in 2012, competing in 6 out of the 8 races on the circuit.