O'Malley may refer to:
- Martin O'Malley, American politician and 61st Governor of Maryland.
- Martin O'Malley, Canadian journalist.
- Charles O'Malley, an eponymous character in a novel by Charles Lever.
- O'Malley (surname), people with the surname O'Malley
- Ó Máille clan, an Irish clan name anglicized as O'Malley
- O'Malley, Australian Capital Territory, a suburb of Canberra
- O'Malley, a fictional character in the machinima series Red vs. Blue
- Abraham de Lacy Giuseppe Casey Thomas O'Malley, a fictional character in the film Aristocats
- Father Charles "Chuck" O'Malley, a fictional character in the films Going My Way and The Bells of St. Mary, and the TV series Going My Way (TV series)
- Nellie O'Malley, a fictional character in American Girl's Samantha sub-series.