Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Third Creek | Stream | | Madison | 45 39 55 N | 112 23 45 W |
| Third Creek | Stream | | Phillips | 47 44 36 N | 107 46 49 W |
| Third Creek | Stream | | Phillips | 48 21 30 N | 107 18 05 W |
| Third Creek | Stream | | Powder River | 45 30 25 N | 105 37 27 W |
| Third Creek | Stream | | Powder River | 45 22 52 N | 105 26 58 W |
| Third Crossing (historical) | Locale | 756 | Sanders | 47 20 10 N | 114 38 48 W |
| Third Gulch | Valley | | Lewis and Clark | 47 02 45 N | 112 25 54 W |
| Third Gully Ski Trail | Trail | 2365 | Madison | 45 16 51 N | 111 24 24 W |
| Third Hay Creek | Stream | | Richland | 47 49 15 N | 104 03 09 W |
| Third Point School (historical) | School | 686 | Valley | 47 53 33 N | 106 31 15 W |
| Third Ridge | Ridge | 735 | Valley | 47 54 13 N | 106 36 18 W |
| Third Slough | Stream | | Madison | 45 33 27 N | 112 20 15 W |
| Third Stooges Dam | Dam | 1440 | Meagher | 46 28 42 N | 110 17 21 W |
| Third Street Ski Trail | Trail | 2528 | Carbon | 45 11 15 N | 109 21 03 W |
| Third Term Mine | Mine | 1802 | Powell | 46 30 11 N | 112 21 09 W |
| Third Term Mine | Mine | 1759 | Powell | 46 30 08 N | 112 21 12 W |
| Third Yellow Mule Creek | Stream | | Madison | 45 14 14 N | 111 24 40 W |
| Thirsty Lake | Lake | 896 | Lincoln | 48 50 49 N | 115 03 22 W |
| Thirsty Mountain | Summit | 1901 | Lincoln | 48 49 11 N | 115 23 18 W |
| Thirteen Flat School (historical) | School | 762 | Prairie | 46 40 36 N | 105 01 35 W |
| Thirteen Gulch | Valley | | Sanders | 47 52 45 N | 115 21 20 W |
| Thirteen Gulch | Valley | | Sanders | 48 00 48 N | 115 47 43 W |
| Thirteenmile Creek | Stream | | Dawson | 47 16 33 N | 104 33 07 W |
| Thirthmile Reservoir Dam | Dam | 716 | Blaine | 48 31 06 N | 108 44 27 W |
| Thirty Mile (historical) | Locale | 1077 | Musselshell | 46 11 35 N | 108 27 06 W |
| Thirtymile Creek | Stream | | Blaine | 48 29 48 N | 108 42 20 W |
| Thirtymile Ranch | Locale | 1077 | Musselshell | 46 11 35 N | 108 27 06 W |
| Thirtymile Reservoir | Reservoir | 716 | Blaine | 48 31 05 N | 108 44 29 W |
| Thistle (historical) | Locale | 1501 | Jefferson | 46 21 15 N | 112 02 43 W |
| Thoeny | Populated Place | 756 | Valley | 48 52 37 N | 106 55 03 W |
| Thoeny Hills | Range | 945 | Phillips | 48 53 32 N | 107 22 15 W |
| Thoeny Post Office (historical) | Post Office | 755 | Valley | 48 52 38 N | 106 54 58 W |
| Thoeny School (historical) | School | 752 | Valley | 48 52 48 N | 106 54 28 W |
| Thoit Coulee | Valley | | Valley | 47 41 22 N | 107 16 36 W |
| Thoma Creek | Stream | | Flathead | 48 56 02 N | 114 32 12 W |
| Thoma Lookout | Locale | 2157 | Flathead | 48 57 42 N | 114 32 55 W |
| Thomae Ranch | Locale | 1815 | Park | 45 33 44 N | 110 48 31 W |
| Thomas B Quaw Elementary School | School | 1356 | Gallatin | 45 46 49 N | 111 10 26 W |
| Thomas Butte | Summit | 920 | Garfield | 47 01 27 N | 107 33 59 W |
| Thomas Coulee | Valley | | Phillips | 48 22 50 N | 107 31 16 W |
| Thomas Creek | Stream | | Meagher | 46 28 34 N | 110 30 03 W |
| Thomas Creek | Stream | | Meagher | 46 42 19 N | 111 11 36 W |
| Thomas Creek Mine | Mine | 1550 | Meagher | 46 40 24 N | 111 18 05 W |
| Thomas Dam | Dam | 729 | Sheridan | 48 46 12 N | 104 15 44 W |
| Thomas Draw | Valley | | Powder River | 45 33 29 N | 106 07 51 W |
| Thomas Draw Well | Well | 988 | Powder River | 45 32 38 N | 106 06 25 W |
| Thomas Francis Meagher Statue | Park | 1257 | Lewis and Clark | 46 35 11 N | 112 01 06 W |
| Thomas Massacre Graves Historical | Cemetery | 1178 | Sweet Grass | 45 44 07 N | 109 42 52 W |
| Thomas McKay/Hobo Mine | Mine | 1843 | Granite | 46 19 57 N | 113 15 42 W |
| Thomas Moore School | School | 1490 | Park | 45 22 13 N | 110 44 01 W |
| Thomas Party Historical Marker | Park | 1189 | Sweet Grass | 45 44 08 N | 109 45 26 W |
| Thomas Post Office (historical) | Post Office | 808 | Dawson | 47 19 04 N | 104 55 40 W |
| Thomas Post Office (historical) | Post Office | 1009 | Missoula | 46 58 37 N | 114 07 21 W |
| Thomas Ranch | Locale | 835 | Garfield | 47 11 45 N | 107 46 45 W |
| Thomas Reservoir | Reservoir | 752 | Garfield | 47 25 36 N | 106 27 37 W |
| Thomas School (historical) | School | 906 | Garfield | 47 01 52 N | 107 33 53 W |
| Thomas Spring | Spring | 1197 | Powder River | 45 37 33 N | 105 58 26 W |
| Thomas Williamson Ditch | Canal | 1189 | Pondera | 48 19 54 N | 112 31 23 W |
| Thomasville (historical) | Populated Place | 1452 | Gallatin | 45 49 48 N | 111 02 33 W |
| Thompson Chain of Lakes Fishing Access Site | Locale | 1250 | Flathead | 48 02 43 N | 114 50 54 W |
| Thompson Chain of Lakes Fishing Access Site | Locale | 1016 | Lincoln | 48 03 46 N | 115 07 47 W |
| Thompson Coulee | Valley | | Fergus | 47 31 36 N | 108 56 08 W |
| Thompson Coulee | Valley | | Garfield | 47 31 21 N | 106 22 58 W |
| Thompson Creek | Stream | | Beaverhead | 44 40 08 N | 112 50 54 W |
| Thompson Creek | Stream | | Beaverhead | 45 44 45 N | 113 30 02 W |
| Thompson Creek | Stream | | Big Horn | 45 28 14 N | 106 59 55 W |
| Thompson Creek | Stream | | Broadwater | 46 43 40 N | 111 29 57 W |
| Thompson Creek | Stream | | Carter | 45 20 58 N | 104 04 32 W |
| Thompson Creek | Stream | | Carter | 45 00 02 N | 104 53 21 W |
| Thompson Creek | Stream | | Carter | 45 20 57 N | 104 04 32 W |
| Thompson Creek | Stream | | Custer | 46 40 29 N | 105 53 29 W |
| Thompson Creek | Stream | | Flathead | 48 32 53 N | 113 37 10 W |
| Thompson Creek | Stream | | Gallatin | 45 50 17 N | 111 09 35 W |
| Thompson Creek | Stream | | Garfield | 47 03 46 N | 106 24 44 W |
| Thompson Creek | Stream | | Mineral | 46 52 54 N | 114 41 08 W |
| Thompson Creek | Stream | | Mineral | 47 11 59 N | 114 54 57 W |
| Thompson Creek | Stream | | Park | 45 12 33 N | 110 34 32 W |
| Thompson Creek | Stream | | Powder River | 45 05 23 N | 105 51 21 W |
| Thompson Creek Mine | Mine | 1586 | Broadwater | 46 43 48 N | 111 30 02 W |
| Thompson Ditch | Canal | 1197 | Carbon | 45 03 32 N | 107 21 53 W |
| Thompson Ditch | Canal | 1477 | Madison | 45 27 43 N | 112 14 56 W |
| Thompson Drain | Canal | 1158 | Teton | 47 42 13 N | 111 46 24 W |
| Thompson Draw | Valley | | Powder River | 45 11 06 N | 106 01 59 W |
| Thompson Falls | Locale | 739 | Sanders | 47 35 40 N | 115 20 49 W |
| Thompson Falls | Populated Place | 779 | Sanders | 47 35 50 N | 115 20 40 W |
| Thompson Falls Airport | Airport | 754 | Sanders | 47 34 29 N | 115 17 07 W |
| Thompson Falls Alliance Church | Church | 779 | Sanders | 47 35 50 N | 115 20 40 W |
| Thompson Falls Campground | Locale | 724 | Sanders | 47 37 05 N | 115 23 17 W |
| Thompson Falls Christian Church | Church | 761 | Sanders | 47 35 42 N | 115 20 04 W |
| Thompson Falls Clinic | Hospital | 779 | Sanders | 47 35 50 N | 115 20 40 W |
| Thompson Falls Dam | Dam | 722 | Sanders | 47 35 18 N | 115 21 16 W |
| Thompson Falls Dam | Dam | 712 | Sanders | 47 35 28 N | 115 21 04 W |
| Thompson Falls Dam Point of Interest | Locale | 722 | Sanders | 47 35 35 N | 115 21 34 W |
| Thompson Falls Elementary School | School | 784 | Sanders | 47 35 52 N | 115 20 41 W |
| Thompson Falls Golf Club | Locale | 720 | Sanders | 47 37 38 N | 115 23 59 W |
| Thompson Falls High School | School | 747 | Sanders | 47 35 43 N | 115 19 19 W |
| Thompson Falls Historical Marker | Park | 738 | Sanders | 47 35 28 N | 115 19 27 W |
| Thompson Falls Junior High School | School | 781 | Sanders | 47 35 51 N | 115 20 37 W |
| Thompson Falls Police Department | Building | 779 | Sanders | 47 35 50 N | 115 20 40 W |
| Thompson Falls Post Office | Post Office | 740 | Sanders | 47 35 44 N | 115 21 09 W |
| Thompson Falls Public Library | Building | 738 | Sanders | 47 35 40 N | 115 20 54 W |
| Thompson Falls Reservoir | Reservoir | 906 | Sanders | 47 36 21 N | 115 17 59 W |
| Thompson Falls Rural Fire Station | Building | 779 | Sanders | 47 35 50 N | 115 20 40 W |
| Thompson Falls State Park Campground | Locale | 721 | Sanders | 47 37 05 N | 115 23 19 W |
| Thompson Falls State Recreation Area | Park | 712 | Sanders | 47 37 03 N | 115 23 29 W |
| Thompson Field | Park | 900 | Flathead | 48 11 30 N | 114 17 56 W |
| Thompson Flats | Flat | 1880 | Lewis and Clark | 46 41 42 N | 112 21 58 W |
| Thompson Gulch | Valley | | Deer Lodge | 45 53 07 N | 113 15 39 W |
| Thompson Gulch | Valley | | Meagher | 46 36 37 N | 111 05 22 W |
| Thompson Gulch Guard Station | Locale | 1927 | Meagher | 46 31 06 N | 111 12 45 W |