| Official Name: | Tvarditsa |
| Subdivision Type: | Country |
| Subdivision Name: | Bulgaria |
| Subdivision Type1: | Provinces (Oblast) |
| Timezone: | EET |
| Utc Offset: | +2 |
| Timezone Dst: | EEST |
| Utc Offset Dst: | +3 |
| Pushpin Map: | Bulgaria |
| Pushpin Map Caption: | Location of Tvarditsa, Bulgaria |
| Pushpin Relief: | 1 |
| Leader Title: | Mayor |
| Postal Code Type: | Postal Code |
| Native Name: | Твърдица |
| Subdivision Name1: | Sliven |
| Population Total: | 5,659 |
| Population As Of: | 2018-12-31 |
| Elevation M: | 396 |
| Postal Code: | 8890 |
| Area Code: | 0454 |
| Blank Info: | CH |
| Blank Name: | License plate |
| Coordinates: | 42.7°N 79°W |
| Leader Name: | Maria Gvozdeikova |
Tvarditsa (Bulgarian: Твърдица in Bulgarian pronounced as /tvɐrˈdit͡sɐ/) is a town in Sliven Province, Southeastern Bulgaria. It is the administrative centre of the homonymous Tvarditsa Municipality. As of December 2018, the town had a population of 5,659.[1]
Tvarditsa is located in the Tvarditsa Valley on the southern slopes of Stara Planina. The area around is known as the Tvarditsa Coal Basin, the only place in the country where soft coal is mined.
Tvarditsa Rocks in the South Shetland Islands, Antarctica are named after Tvarditsa.[2] The Bessarabian Bulgarian village of Tvardiţa in Taraclia District, Moldova, was founded by refugees from Tvardisa, who named it after their ancestral town.[3]
As of December 2018, the town of Tvarditsa has 5,659 inhabitants, while the municipality of Tvarditsa has 13,413 inhabitants. Most inhabitants are ethnic Bulgarians (89%), followed by a large Romani minority (9%). The main faith is Orthodox Christianity.