- O'Bir, Jon (Trance/Progressive-Trance DJ & producer from Nottingham, UK and based in Manchester, UK)
- O'Boy (french rapper)
- O'Boyle, Maeve
- O'Brien Sisters, The
- O'Brien-Docker, Ian
- O'Brien, Charlie (singer and filmmaker)
- O'Brien, Chris (US Singer-songwriter)
- O'Brien, Joseph (production music composer)
- O'Brien, Joseph (Christian Artist)
- O'Brien, Michael (US AOR/christian vocalist)
- O'Brien, Mick & Ó Raghallaigh, Caoimhín
- O'Brien, Mick agus Ó Raghallaigh, Caoimhín
- O'Brien, Mollie
- O'Brien, Paul
- O'Brien, Paul, The, All Stars Band
- O'Brien, Sinead (Irish punk poet)
- O'Brien, Tim & Scott, Darrell
- O'Brien, Tim & Scott, Darrell
- O'Bros (O'Bros from Munich, Germany)
- O'Callaghan, John & Larkin, Betsie
- O'Callaghan, John feat. Cathy Burton
- O'Callaghan, Patricia
- O'Clock, Apes
- O'Connor, Geoffrey
- O'Connor, Hazel
- O'Connor, Katie (Songwriter from Galway, Ireland)
- O'Connor, Mark & Daniels, Charlie
- O'Connor, Mark's Hot Swing Trio
- O'Connor, Nora
- O'Connor, Tony (New Age composer)
- O'Day, Anita & Tjader, Cal
- O'Day, Anita with May, Billy
- O'Day, Aubrey
- O'Doherty, David
- O'Donis, Colby feat. Akon
- O'Donnell, Daniel & Duff, Mary
- O'Dowd, Erin
- O'Flaherty, Jack (Jack Fla)
- O'funk'illo
- O'Hara, Eureka
- O'Hara, Helen
- O'Hara, Maureen
- O'Hara, Page & Portman, Rachel
- O'Hara, Paige, Benson, Robby, Orbach, Jerry, Lansbury, Angela and Stiers, David Ogden
- O'Hara, Paige, Peters, Bernadette
- O'Hara, Paige, White, Richard and Chorus
- O'Hearn, Patrick (American drummer and percussionist)
- O'Hooley & Tidow
- O'Kane, Damien (Northern Irish folk musician)
- O'Keefe, Laurence (British bassist of Jazz Butcher, Levitation & Dark Star)
- O'Landa Draper and Associates, The
- O'Malley, Lenore
- O'May, Pat (French musician)
- O'Neal, Jamie
- O'Neal, Juliana
- O'Neill Brothers, The (Tim & Ryan)
- O'Neill, David (Christian Trumpet Artist)
- O'Neill, Lisa (Irish singer)
- O'Neill, Megan
- O'o (French pop duo)
- O'Reilly, Emmett
- O'Reilly, Lorkin
- O'Reilly, Noel (Active since 2019)
- O'Reilly, Ryan (the band)
- O'Ryan (Irish Musician)
- O's, The (Dallas bluegrass duo)
- O'Shine, Simon & Navel, Adam
- O'Shine, Simon & Romel, Ahmed
- O'Sullivan, Camille
- O'Sullivan, Gilbert feat. Lee, Peggy
- O'Yaba
- O’, Gary (Canadian singer‐songwriter Gary O’Connor)
- O’Banion, John
- O’Beirne, Gerry (Irish guitarist)
- O’Brien, Dermot
- O’Brien, Hod
- O’Brien, Kevin James
- O’Brien, Kyle
- O’Brien, Olivia
- O’Brien, Olivia feat. FLETCHER
- O’Brien, Richard
- O’Brien, Soledad (American broadcast journalist)
- O’Brien, Tim (US bluegrass musician)
- O’Brien, Tim & Scott, Darrell
- O’Brother
- O’Bryan
- O’Byrne, Lucy (Soprano)
- O’Callaghan, John (trance DJ/producer/artist)
- O’Callaghan, John & Gallagher, Audrey
- O’Callaghan, John & Gallagher, Kathryn
