It will be 24-year-old O'Callaghan's first Test start after winning all eight of his previous caps off the bench. He teams up with Munster second-row colleague Paul O'Connell.
Maggs and O'Kelly drop down to replacement duty, and there is no place in the 22 for Munster wing Anthony Horgan, who went on as a second-half substitute in Paris.
Ireland are bidding for a fifth successive victory over Wales.
Ireland team to play Wales in the RBS 6 Nations Championship at Lansdowne Road, Dublin: G Dempsey (Leinster); S Horgan (Leinster), G D'Arcy (Leinster), B O'Driscoll (Leinster, capt), T Howe (Ulster); R O'Gara (Munster), P Stringer (Munster); R Corrigan (Leinster), S Byrne (Leinster), J Hayes (Munster), D O'Callaghan (Munster), P O'Connell (Munster), S Easterby (Llanelli Scarlets), K Gleeson (Leinster), A Foley (Munster).
Replacements: F Sheahan (Munster), S Best (Ulster), M O'Kelly (Leinster), V Costello (Leinster), G Easterby (Rotherham), D Humphreys (Ulster), K Maggs (Bath).
Before Will Greenwood started breaking down moves off the field, he was doing the business on it - and no match better illustrated the type of marauding centre he was than in a virtuoso performance against Wales.