| # | Name | Elo | Total | Country | Rank |
| 3851. | okronos | 1552 | 1 | - | |
| 3852. | old hand | 2512 | 260 | Beginner | |
| 3853. | oldbone | 2052 | 284 | - | |
| 3854. | oldie58 | 2228 | 5025 | FIDE Master | |
| 3855. | oldtop | 2040 | 12756 | Top Player | |
| 3856. | oldwilly | 2370 | 15289 |
|
FIDE Master |
| 3857. | oleh 75 | 1843 | 21 | Beginner | |
| 3858. | olga 2005 | 2726 | 7566 | Grandmaster | |
| 3859. | olieshakki | 2045 | 50 | Beginner | |
| 3860. | oligarxus | 2601 | 664 | Amateur | |
| 3861. | oliver 123 | 2320 | 12153 | FIDE Master | |
| 3862. | oliver becker | 2721 | 36253 |
|
Grandmaster |
| 3863. | oliver reeh | 2933 | 359024 | World Champion | |
| 3864. | oliver_beyond | 2060 | 120 | Strong Amateur | |
| 3865. | olowolayemo | 1962 | 31 | Beginner | |
| 3866. | olyver | 1581 | 2 | - | |
| 3867. | om_patel_fide | 2158 | 192 | Strong Amateur | |
| 3868. | omarsh12f | 1664 | 3 | - | |
| 3869. | omarttrtt | 1767 | 67 | Beginner | |
| 3870. | omelnychenko | 1849 | 33 | Beginner | |
| 3871. | omikaelcx | 1597 | 3 | - | |
| 3872. | omirc | 1651 | 2 | - | |
| 3873. | omkar5 | 2068 | 421 | Talent | |
| 3874. | omkargopikrishna | 2290 | 435 | Talent | |
| 3875. | omtaga | 1901 | 69 | Beginner |
| # | Name | Elo | Total | Country | Rank |
| 3876. | omverma788 | 2004 | 760 | Shooting Star | |
| 3877. | onam | 1988 | 88 | - | |
| 3878. | onemunja | 2272 | 388 | Strong Apprentice | |
| 3879. | onkel3000 | 1979 | 1504 | Tactics Master | |
| 3880. | onkeluf | 2165 | 195 | - | |
| 3881. | onnootje | 2558 | 6432 | Internat. Master | |
| 3882. | onshi | 1942 | 548 | Talent | |
| 3883. | oo_jms_oo | 1791 | 30 | Beginner | |
| 3884. | op1808 | 2156 | 88 | Amateur | |
| 3885. | opa304 | 2435 | 109607 | Internat. Master | |
| 3886. | ophr158 | 2153 | 2052 | Top Player | |
| 3887. | orangetulip | 1553 | 81 | - | |
| 3888. | orbanandreas | 2393 | 217 | - | |
| 3889. | orbcom | 1854 | 55 | Beginner | |
| 3890. | orebrook | 2416 | 2555 |
|
FIDE Master |
| 3891. | orestes40 | 1725 | 24 | Beginner | |
| 3892. | orfanidis haris | 1671 | 3 | - | |
| 3893. | organicponytail | 2110 | 355 | Beginner | |
| 3894. | orhan galip ozdemir | 1712 | 14 | - | |
| 3895. | orlock936 | 1833 | 1854 | Attacking Player | |
| 3896. | orpheus | 1852 | 39 | Beginner | |
| 3897. | orsito60 | 1921 | 123 |
|
Strong Amateur |
| 3898. | ortizfran9 | 2018 | 37 | Beginner | |
| 3899. | osita241 | 1897 | 75 |
|
Beginner |
| 3900. | oskarchess | 2519 | 1954 | - |