Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| One River Place Colonia | Populated Place | 127 | Webb | 27 24 12 N | 099 29 03 W |
| One Sixty Four Place Airport | Airport | 356 | Jack | 33 07 10 N | 098 13 51 W |
| One Stop Multiservice High School | School | 43 | Hidalgo | 26 12 56 N | 098 19 39 W |
| One'ness Church | Church | 187 | Dallas | 32 37 25 N | 096 47 47 W |
| Oneal Cemetery | Cemetery | 389 | Lampasas | 31 19 57 N | 098 19 30 W |
| Oneal Lake | Reservoir | 19 | Liberty | 30 27 25 N | 094 51 19 W |
| Oneal Lake Dam | Dam | 19 | Liberty | 30 27 25 N | 094 51 19 W |
| Oneill Cemetery | Cemetery | 110 | Gonzales | 29 25 14 N | 097 44 28 W |
| Onemile Creek | Stream | | Henderson | 32 14 18 N | 095 52 48 W |
| Onemile Lake | Lake | 732 | Howard | 32 15 09 N | 101 29 53 W |
| Onemile Tank | Reservoir | 1205 | Culberson | 31 09 51 N | 104 33 12 W |
| Onesimo Hernandez Elementary School | School | 141 | Dallas | 32 49 12 N | 096 50 08 W |
| Onion Bayou | Stream | | Chambers | 29 34 49 N | 094 29 32 W |
| Onion Branch | Stream | | Parker | 32 34 02 N | 097 56 48 W |
| Onion Branch | Stream | | Williamson | 30 30 56 N | 097 40 19 W |
| Onion Creek | Populated Place | 118 | Ellis | 32 13 28 N | 096 37 18 W |
| Onion Creek | Populated Place | 175 | Travis | 30 08 12 N | 097 47 03 W |
| Onion Creek | Stream | | Archer | 33 40 03 N | 098 30 01 W |
| Onion Creek | Stream | | Bell | 30 59 43 N | 097 40 59 W |
| Onion Creek | Stream | | Coryell | 31 20 32 N | 097 29 20 W |
| Onion Creek | Stream | | Ellis | 32 12 59 N | 096 36 30 W |
| Onion Creek | Stream | | Gillespie | 30 29 32 N | 099 06 55 W |
| Onion Creek | Stream | | McCulloch | 31 06 21 N | 099 10 40 W |
| Onion Creek | Stream | | Travis | 30 12 21 N | 097 35 16 W |
| Onion Creek | Stream | | Uvalde | 29 30 50 N | 099 30 40 W |
| Onion Creek Lodge | Locale | 240 | Hays | 30 04 29 N | 097 54 53 W |
| Onion Creek Park | Park | 160 | Travis | 30 10 01 N | 097 44 54 W |
| Onion Creek School | School | 530 | Gillespie | 30 28 54 N | 099 09 54 W |
| Onion Creek Trail | Trail | 159 | Travis | 30 11 02 N | 097 43 38 W |
| Onion Flat | Flat | 1017 | Brewster | 29 24 15 N | 103 21 28 W |
| Onion Spring | Populated Place | 1018 | Brewster | 29 24 01 N | 103 20 02 W |
| Onion Spring | Spring | 1018 | Brewster | 29 24 05 N | 103 19 51 W |
| Onion Spring | Spring | 1485 | Jeff Davis | 30 59 29 N | 104 06 27 W |
| Onion Top | Summit | 426 | Lampasas | 31 16 43 N | 098 15 00 W |
| Onslow Park | Park | 197 | Bexar | 29 25 54 N | 098 26 41 W |
| Onstot Cemetery | Cemetery | 171 | Hunt | 33 16 55 N | 096 01 46 W |
| Onstott Branch | Stream | | Fannin | 33 38 18 N | 096 06 36 W |
| Onstott Cemetery | Cemetery | 168 | Fannin | 33 37 22 N | 096 01 47 W |
| Opal Cemetery | Cemetery | 260 | Wise | 33 00 22 N | 097 39 12 W |
| Opdyke | Populated Place | 1057 | Hockley | 33 35 35 N | 102 16 32 W |
| Opdyke West | Populated Place | 1058 | Hockley | 33 35 32 N | 102 18 09 W |
| Opelika | Populated Place | 128 | Henderson | 32 17 50 N | 095 40 28 W |
| Opelika Gas Field | Oilfield | 146 | Henderson | 32 19 53 N | 095 42 21 W |
| Open Air Church | Church | 163 | Collin | 33 05 16 N | 096 32 26 W |
| Open Arms Fellowship Church | Church | 203 | Tarrant | 32 48 43 N | 097 26 14 W |
| Open Arms United Methodist Church | Church | 215 | Bell | 31 05 45 N | 097 20 33 W |
| Open Bible Fellowship Church | Church | 180 | Collin | 33 01 31 N | 096 40 42 W |
| Open Bottom Creek | Stream | | Polk | 30 50 56 N | 095 07 35 W |
| Open Door Baptist Church | Church | 141 | Dallas | 32 45 10 N | 096 35 47 W |
| Open Door Baptist Church | Church | 152 | Rusk | 32 09 18 N | 094 48 03 W |
| Open Door Baptist Church | Church | 172 | Tarrant | 32 41 53 N | 097 02 24 W |
| Open Door Church | Church | 153 | Dallas | 32 44 04 N | 096 38 46 W |
| Open Door Church | Church | 122 | Gregg | 32 30 59 N | 094 48 19 W |
| Open Door Church of God in Christ | Church | 987 | Gray | 35 31 27 N | 100 57 32 W |
| Open Door Church of God in Christ | Church | 126 | Navarro | 32 05 47 N | 096 27 08 W |
| Open Door Church of God in Christ | Church | 168 | Travis | 30 16 38 N | 097 41 57 W |
| Open Door Community Church | Church | 221 | Bell | 31 05 29 N | 097 20 59 W |
| Open Door Fellowship Church | Church | 178 | Tarrant | 32 48 11 N | 097 17 26 W |
| Open Door Missionary Baptist Church | Church | 21 | Harris | 29 53 41 N | 095 18 48 W |
| Open Door Pentecostal Church | Church | 189 | Bexar | 29 24 54 N | 098 25 54 W |
| Open Gate Church of the Nazarene | Church | 1196 | El Paso | 31 53 34 N | 106 24 24 W |
| Open Hollow | Valley | | Edwards | 29 55 41 N | 100 02 04 W |
| Open Hollow | Valley | | Uvalde | 29 29 10 N | 100 06 40 W |
| Open Hollow | Valley | | Val Verde | 29 54 38 N | 100 51 23 W |
| Open Lakes | Lake | 1 | Chambers | 29 36 59 N | 094 34 03 W |
| Open Mine Hill | Summit | | Brewster | 30 09 26 N | 103 36 09 W |
| Open Tank | Reservoir | 113 | Atascosa | 28 41 21 N | 098 31 14 W |
| Open Tank Windmill | Locale | 873 | Midland | 31 58 14 N | 102 09 54 W |
| Opendoor Church of God in Christ | Church | 14 | Harris | 29 47 23 N | 095 19 57 W |
| Operating Basin Number 1 | Reservoir | 8 | Calhoun | 28 29 49 N | 096 46 13 W |
| Operating Basin Number 1 Levee | Dam | 28 | Calhoun | 28 29 48 N | 096 46 12 W |
| Operating Basin Number 31 | Reservoir | 8 | Calhoun | 28 30 55 N | 096 46 25 W |
| Operating Basin Number 31 Levee | Dam | 8 | Calhoun | 28 30 55 N | 096 46 25 W |
| Operating Basin Number 4 | Reservoir | 7 | Calhoun | 28 30 19 N | 096 45 25 W |
| Operating Basin Number 4 Levee | Dam | 7 | Calhoun | 28 30 19 N | 096 45 25 W |
| Operating Basin Number 5 | Reservoir | 8 | Calhoun | 28 31 19 N | 096 45 37 W |
| Operating Basin Number 5 Levee | Dam | 8 | Calhoun | 28 31 19 N | 096 45 37 W |
| Operation Reach Christ Community Fellowship Church | Church | 25 | Harris | 29 51 31 N | 095 24 36 W |
| Oplin | Populated Place | 604 | Callahan | 32 08 19 N | 099 33 31 W |
| Opossum Branch | Stream | | Somervell | 32 15 01 N | 097 49 10 W |
| Opossum Creek | Stream | | McMullen | 28 29 45 N | 098 21 14 W |
| Opossum Creek | Stream | | Medina | 29 23 53 N | 098 56 55 W |
| Opossum Creek | Stream | | Washington | 30 09 45 N | 096 30 28 W |
| Opossum Creek | Stream | | Williamson | 30 42 04 N | 097 26 59 W |
| Opossum Hill | Summit | 113 | McMullen | 28 33 59 N | 098 23 35 W |
| Opossum Hill Tank | Reservoir | 79 | McMullen | 28 34 01 N | 098 23 48 W |
| Opossum Hollow | Valley | | Cooke | 33 45 35 N | 097 18 47 W |
| Opossum Hollow | Valley | | Johnson | 32 10 26 N | 097 28 40 W |
| Opossum Hollow | Valley | | Live Oak | 28 29 35 N | 098 17 19 W |
| Opossum Hollow | Valley | | Somervell | 32 15 43 N | 097 49 30 W |
| Opossum Trot Church | Church | 83 | Bowie | 33 21 08 N | 094 09 12 W |
| Opp Cemetery | Cemetery | 623 | Menard | 30 51 55 N | 100 00 30 W |
| Opp Spring | Spring | 636 | Menard | 30 51 36 N | 100 00 40 W |
| Oppe Elementary School | School | 2 | Galveston | 29 17 09 N | 094 51 40 W |
| Oppenheimer Canyon | Valley | | Val Verde | 30 05 14 N | 101 31 03 W |
| Opportunity Center School | School | 112 | Harrison | 32 32 19 N | 094 22 21 W |
| Opportunity Church of God and Christ | Church | 124 | Dallas | 32 45 07 N | 096 44 54 W |
| Opportunity Learning Center - China Spring | School | 168 | McLennan | 31 38 09 N | 097 16 44 W |
| Opportunity Learning Center - Lorena | School | 143 | McLennan | 31 38 08 N | 097 05 04 W |
| Opportunity Learning Center - Mart | School | 161 | McLennan | 31 32 30 N | 096 49 46 W |
| Opportunity Learning Center - West | School | 195 | McLennan | 31 48 35 N | 097 05 32 W |
| Opportunity Park | Park | 125 | Dallas | 32 45 49 N | 096 45 17 W |
| Optimist Camp | Locale | 4 | Chambers | 29 41 09 N | 094 51 60 W |
| Optimist Number 1 Field | Park | 228 | Bell | 31 06 44 N | 097 20 43 W |
| Optimist Park | Park | 212 | Bell | 31 09 11 N | 097 26 36 W |
| Optimist Park | Park | 897 | Ector | 31 53 07 N | 102 21 08 W |
| Optimist Ponds | Lake | 20 | Victoria | 28 49 11 N | 097 01 25 W |
| Options in Education High School | School | 36 | Hidalgo | 26 12 39 N | 098 14 29 W |
| Options School - Waco | School | 159 | McLennan | 31 35 17 N | 097 10 48 W |
| Ora | Populated Place | 60 | Angelina | 31 16 39 N | 094 25 40 W |