Raishaan O. -- Peter Olszowka

1. O., Raishaan (2)
2. O., Ziri (2)
3. Oakes, Ron (23)
4. Oakes, Tara (5)
5. Oakley, Annie (4)
6. O'Bar, Rob (5)
7. Obrcian, Kornel (3)
8. O'Brien, Beth (3)
9. O'Brien, Hal (7)
10. O'Brien, Kevin
11. O'Brien, Kristen
12. O'Brien, Terry
13. O'Brien, Ulrika (6)
14. Oceana, Esteban (2)
15. Oceanna (2)
16. Ochipinti, Dan
17. Ochoa, Erica (3)
18. Ochoa, Esmeralda
19. Ochoa, Johan
20. O'Connell, Consuelo
21. O'Connell, Jennifer (2)
22. O'Connell, Michael
23. O'Connell, Wendy
24. O'Conner, Grayson (2)
25. O'Connor, Dea
26. O'Connor, Edward (2)
27. O'Connor, Shannon
28. O'Darrow, Heather (4)
29. Odayashi, Kyra (4)
30. Odbert, Elspeth
31. Odbert, Jim
32. O'Deay, Jerry (2)
33. O'Dell, Tom
34. O'Donnell, Abby (3)
35. Ofoegbu, Ike
36. Oggy (2)
37. Ogre (6)
38. Oh, Stan (137)
39. O'Halloran, Christina (35)
40. O'Halloran, John (53)
41. Ohanesian, Liz
42. O'Hanlon, Rod
43. O'Hare, Dorothy (11)
44. O'Higgins, Kristopher
45. Ohlde, Robert
46. Ohlson, LeraRae
47. Ohlson, Nancy (2)
48. Okamura, David (14)
49. Oki-Dogs
50. Okkami, Paige (2)
51. Okum, Allan (4)
52. Oldroyd, Paul (13)
53. Oliansky, Ingrid (14)
54. Oliver, Erin (4)
55. Oliver, Gloria (2)
56. Oliver, John W. (4)
57. Oliver, Kathie (8)
58. Oliver, Thomas (17)
59. Oliver, Tom (2)
60. Olsen, David
61. Olsen, John
62. Olsen, Justin
63. Olsen, Karina (2)
64. Olsen, Kim
65. Olsen, Tammy (4)
66. Olson, Bill
67. Olson, Erik V. (95)
68. Olson, Glen (96)
69. Olson, Janis (152)
70. Olson, Jonathan (46)
71. Olson, Mark (22)
72. Olson, Priscilla (21)
73. Olszowka, Peter

Matt O'Malley -- Lance Oszko

74. O'Malley, Matt
75. O'Meara, Jennifer (2)
76. Omnii (2)
77. Ondoy, Carlo (11)
78. One, Surly
79. O'Neil, Paul (2)
80. O'Neil, Raven (9)
81. O'Neill, Dave (2)
82. O'Neill, Jack
83. Oni-chan
84. Oniko
85. Ono, Kenji
86. Ontell, Ron (47)
87. Ontell, Val (30)
88. Onyx (14)
89. Ood (2)
90. Ookami
91. Orantes, Anthony (2)
92. Orchid, Purple
93. O'Rear, Victor
94. Orenji-san
95. Orenstein, Liz
96. Organ-Kean, Margaret
97. O'Riley, Rod (26)
98. Ormsby-Olivares, Rocky
99. Orochimaru (41)
100. Oropallo, Brandon
101. Oropesa, Samatha (3)
102. Orozco, Erik
103. Orr, Jordan (3)
104. Orr, Marilee (9)
105. Orrock, Alec (347)
106. Ortega, Alex
107. Ortega, Angel
108. Ortega, Manuel
109. Ortega, Riley
110. Ortega, Vicki (2)
111. Orth, Eric (2)
112. Orth, Jeff (50)
113. Ortiz, Erica (5)
114. Ory, Alex (2)
115. Orzechowski, Tom
116. Osaki, Nana
117. Osborn, Josh
118. Osborn, Phil
119. Osborne, Cary (7)
120. Osborne, Heather (6)
121. Osborne, Jason (4)
122. Osborne, Jonathan
123. Osborne, Kay Selover (2)
124. O'Shea, Chris (6)
125. O'Shea, Dick (4)
126. O'Shea, Kaity (5)
127. O'Shea, Tara
128. Oshima, Dale
129. Oshins, Keith (2)
130. Oshiro, Mark (2)
131. Osier, Henry (2)
132. Osterholm, Amy
133. Ostro, Marie (3)
134. Ostro, Shelley (2)
135. Oszko, Lance (2)

Jayme Ota -- Ozzy

136. Ota, Jayme
137. Otakon (5)
138. Otero, Marvin
139. O Tuama, Aodh Og
140. Oun, Charlie
141. Oung, Miky (0)
142. Outlaw, Da (40)
143. Outlaw, Sick Girl
144. Ouw, Nadia (2)
145. Ouw, Shirley (2)
146. Ovary, Madame
147. Overton, Kathi (7)
148. Ovitt, Alexandra (2)
149. Owen, Brandi
150. Owen, Caroline (9)
151. Owen, Diana
152. Owen, Eric (3)
153. Owen, Ralph (8)
154. Owens, Aurora (10)
155. Owens, Eric (9)
156. Owens, Kendra
157. Owens, Scott
158. Owings, Jul (5)
159. Owings, Mark (2)
160. Oxford, Helen (3)
161. Oyama, Noriko (2)
162. Oyster, Royster T. (2)
163. Ozbun, Robert
164. Ozzy (3)

33 first names

Oceanna October Oggy Ogre Oki-Dogs Okie Ol' Olga Olivia (2) Omaha Omar (2) Omnii One Oni-chan Oniko Onyx Ood Ookami Ophelia Orange Orenda Orenji-san Orlando Orletta Orochimaru Orson Oscar (3) Otakon Other Otto Ouran Ozgun (2) Ozzy