Ziri O. -- Omnii

1. O., Ziri (2)
2. Oakes, Ron (7)
3. Oakes, Tara (5)
4. Oakley, Annie (4)
5. O'Bar, Rob (5)
6. O'Brien, Beth (3)
7. O'Brien, Hal (7)
8. O'Brien, Kevin
9. O'Brien, Terry
10. O'Brien, Ulrika (6)
11. Oceana, Esteban (2)
12. Oceanna (2)
13. Ochipinti, Dan
14. Ochoa, Johan
15. O'Connell, Consuelo
16. O'Connell, Jennifer (2)
17. O'Connell, Michael
18. O'Connell, Wendy
19. O'Conner, Grayson (2)
20. O'Connor, Dea
21. O'Connor, Edward (2)
22. O'Connor, Shannon
23. O'Darrow, Heather (4)
24. Odayashi, Kyra (4)
25. Odbert, Elspeth
26. Odbert, Jim
27. O'Deay, Jerry (2)
28. O'Dell, Tom
29. O'Donnell, Abby (3)
30. Ofoegbu, Ike
31. Oggy (2)
32. Ogre (6)
33. Oh, Stan (125)
34. O'Halloran, Christina (14)
35. O'Halloran, John (20)
36. O'Hanlon, Rod
37. O'Hare, Dorothy (6)
38. O'Higgins, Kristopher
39. Ohlde, Robert
40. Ohlson, LeraRae
41. Ohlson, Nancy (2)
42. Okamura, David (8)
43. Oki-Dogs
44. Okkami, Paige (2)
45. Okum, Allan (4)
46. Oldroyd, Paul (13)
47. Oliansky, Ingrid (13)
48. Oliver, Erin (4)
49. Oliver, Gloria (2)
50. Oliver, John W. (4)
51. Oliver, Kathie (8)
52. Oliver, Thomas (16)
53. Oliver, Tom (2)
54. Olsen, David
55. Olsen, John
56. Olsen, Karina (2)
57. Olsen, Kim
58. Olsen, Tammy
59. Olson, Bill
60. Olson, Erik V. (93)
61. Olson, Glen (96)
62. Olson, Janis (133)
63. Olson, Jonathan (46)
64. Olson, Mark (19)
65. Olson, Priscilla (21)
66. O'Malley, Matt
67. O'Meara, Jennifer (2)
68. Omnii (2)

Carlo Ondoy -- Royster T. Oyster

69. Ondoy, Carlo (11)
70. One, Surly
71. O'Neil, Paul (2)
72. O'Neil, Raven (9)
73. O'Neill, Dave (2)
74. O'Neill, Jack
75. Oniko
76. Ono, Kenji
77. Ontell, Ron (40)
78. Ontell, Val (26)
79. Onyx (2)
80. Ookami
81. Orantes, Anthony (2)
82. Orchid, Purple
83. O'Rear, Victor
84. Orenstein, Liz
85. Organ-Kean, Margaret
86. O'Riley, Rod (24)
87. Orochimaru (41)
88. Oropallo, Brandon
89. Oropesa, Samatha (3)
90. Orozco, Erik
91. Orr, Jordan (3)
92. Orr, Marilee (7)
93. Orrock, Alec (66)
94. Ortega, Alex
95. Ortega, Angel
96. Ortega, Manuel
97. Ortega, Riley
98. Ortega, Vicki (2)
99. Orth, Jeff (14)
100. Ortiz, Erica (5)
101. Ory, Alex
102. Orzechowski, Tom
103. Osaki, Nana
104. Osborn, Phil
105. Osborne, Cary (7)
106. Osborne, Heather (6)
107. Osborne, Jason (4)
108. Osborne, Jonathan
109. O'Shea, Chris (6)
110. O'Shea, Dick (2)
111. O'Shea, Kaity (5)
112. O'Shea, Tara
113. Oshins, Keith (2)
114. Osier, Henry (2)
115. Ostro, Marie (3)
116. Ostro, Shelley (2)
117. Oszko, Lance (2)
118. Ota, Jayme
119. Otakon (2)
120. Otero, Marvin
121. O Tuama, Aodh Og
122. Oun, Charlie
123. Oung, Miky (0)
124. Outlaw, Da (40)
125. Outlaw, Sick Girl
126. Ouw, Nadia (2)
127. Ouw, Shirley (2)
128. Ovary, Madame
129. Overton, Kathi (7)
130. Ovitt, Alexandra (2)
131. Owen, Brandi
132. Owen, Caroline (9)
133. Owen, Diana
134. Owen, Eric (3)
135. Owen, Ralph (8)
136. Owens, Kendra
137. Owens, Scott
138. Owings, Jul (5)
139. Owings, Mark (2)
140. Oxford, Helen (3)
141. Oyama, Noriko (2)
142. Oyster, Royster T. (2)

Robert Ozbun -- Ozzy

143. Ozbun, Robert
144. Ozzy (3)

28 first names

Oceanna Oggy Ogre Oki-Dogs Okie Ol' Olivia (2) Omaha Omar Omnii One Oniko Onyx Ookami Ophelia Orange Oren Orenda Orlando Orletta Orochimaru Orson Oscar (3) Otakon Otto Ouran Ozgun (2) Ozzy